How to test a relay? (The answer is found)

What is the best way to test a simple relay?

  • To test a relay to see whether it is good or defective, the simplest way to do would be to use a multimeter set to the ohmmeter setting and measure various resistance values of the relay.

How can I test a relay at home?

Here is a few steps of how you can test an automotive relay at home:

  1. Locate the Relay. Before you can test the relay, you need to find it.
  2. Swap the Relay. The simplest way to test the relay is by swapping it with one that is working.
  3. Use a Multimeter. With your multimeter, you can test the relay.
  4. Add Power.
  5. Test Switch.

How do you tell if a relay is bad with a multimeter?

The only tool required to check a relay is a multimeter. With the relay removed from the fuse box, the multimeter set to measure DC voltage and the switch in the cab activated, first check to see if there are 12 volts at the 85 position in the fuse box where the relay plugs in (or wherever the relay is located).

Can you test a relay with a test light?

Use a high impedance test light to test that the relay is receiving power. Probe the wire from the relay to the component it controls. If the bulb lights, then there is power leaving the relay, and it is working properly.

What causes a relay to fail?

In fact, the life of a relay is essentially determined by the life of its contacts. Degradation of contacts is caused from high in-rush currents, high- sustained currents, and from high voltage spikes. Relays can also fail due to poor contact alignment and open coils.

Does a relay click when it’s bad?

If your starter relay has gone bad, the electrical signal will never make it from the battery to the starter motor. As a result, your engine won’t turn over – no matter how many times you turn the key. A faulty relay often produces an audible clicking sound when you turn your car.

Why relay testing is required?

Why is protection relay testing important? Due to the critical nature of protection relays, testing during the commissioning stage is crucial for confidence in the operational safety of an electrical system. Additionally, testing on a regular basis is necessary to ensure correct operation is maintained.

How To Test A Relay

Depositphotos If you purchase a product after clicking on one of our affiliate links, The Drive and its partners may get a commission. More information may be found here. There are several electrical components in your car that power everything from the air conditioner to the taillights. When anything goes wrong with one of those components, it can be difficult to determine the source of the problem. However, when it comes to a vehicle’s electronics, there is a good likelihood that the problem is connected to a relay.

The circuits act as switches, allowing one circuit to control another despite the difference in amperage between the two.

Fortunately, checking a relay is a simple procedure that even inexperienced mechanics can complete.

DepositphotosA fuse and relay box for a vehicle.

Read further

Relay Diagnostics Basics

Estimated time required: 30 minutes to an hour, depending on skill level and the proximity of the relay station Beginner’s level of ability Electrical System of the Vehicle

What Is A Relay?

Many different types of vehicles are equipped with relays; in fact, they are also employed in maritime and aviation applications. The majority of the time, they are utilized to allow a low-amperage circuit to regulate a higher-amperage circuit. Essentially, relays function as switches, allowing the low-amperage circuit to control the high-amperage circuit by turning it on or off. Consider the headlights on your vehicle as an illustration. It is possible that if you connect the lights directly to the on/off switch in the vehicle’s dashboard, the current used by the lights will exceed the switch’s capacity, causing wire melting and even a fire in certain situations.

Relay Safety

Although relay testing is a straightforward procedure, it should not be taken lightly. Taking the following considerations into consideration while dealing with relays is a good idea:

  • In the event that you’ve decided that the relay is faulty and that it has to be changed, it is not acceptable to use relays from other components of the vehicle or from a random rubbish bin in your garage to complete the job. The incorrect relay can result in a short circuit or a power surge, which can cause harm to your vehicle’s electrical system. Handle the relay with care and avoid dropping it if at all possible. If the relay is damaged inside, it might result in the burning or melting of wires and other components. Also, refrain from altering the relay in any way. Relay work or anything involving electricity should not be started when the area around you is filled with potentially flammable or explosive gases, such as gasoline or other fuels. You should always use your vehicle’s service handbook (not the owner’s manual) to identify and comprehend the wiring system and relays, even if you are a seasoned tinkerer in the garage.

Depositphotos An ohmmeter is used to check the relay in an automobile.

Everything You’ll Need To Test a Relay

Depositphotos Test of a car’s relay with an ohmmeter.

Tool List:

  • A test light with a high impedance
  • An ohmmeter – sometimes known as a digital multimeter (DMM) – measures resistance. Service handbook for the vehicle (highly recommended, but not necessary)

Parts List:

It will save you valuable time if you organize your tools and equipment so that everything is conveniently accessible. This will eliminate the need to wait for your handy youngster or four-legged assistant to bring you the sandpaper or blowtorch. (You will not require a blowtorch for this task.) Please do not allow your child to hand you a blowtorch—Ed.) Even if you have a limited amount of garage space and plan to do maintenance and repairs on your car on the street, make sure you are not breaking any laws by doing so.

Every state and municipality has its own set of rules regarding this sort of activity, and we will not assist you in getting your automobile back on the road if things go wrong.

Here’s How To Test a Relay

Let’s get this party started!

  1. Let’s get this show on the road.

Here’s a visual representation of our step-by-step procedure. Step 1 – This is the first step. Mike Bumbeck is a writer and musician who lives in New York City. Mike Bumbeck’s second step is referred to as Step 2. Mike Bumbeck’s Step 3 – Step 3Mike Bumbeck’s Step 3 Step 4 – This is the fourth step. Mike Bumbeck is a writer and musician who lives in New York City. Step 5 – This is the fifth step. Mike Bumbeck is a writer and musician who lives in New York City. Step 6 – This is the sixth step.

Step 7 – This is the seventh step.

Step 8 – This is the eighth step.

You’ve accomplished your goal!

Get Help With Testing a relay From Mechanic On JustAnswer

The Driver understands that, despite the fact that our How-To guides are comprehensive and easy to follow, a rusted bolt, an engine component not in the proper place, or oil gushing everywhere can cause a project to go awry. So we’ve joined with JustAnswer, which links you to licensed mechanics all around the world to help you get through even the most difficult projects on time and on budget. So, if you have a query or are stuck, go here to speak with a mechanic in your local area.

Pro Tips to Test a Relay

Over the years, we at The Drive have put a lot of relays through their paces and discovered that the simplest technique is the best. After all is said and done, here are a few pointers from the professionals.

  • For years, we’ve experimented with many relay designs, and we’ve come to believe that the simplest solution is the most effective. So, here are a few pointers from the professionals to get you started:

FAQs About Testing a Relay

If you have any queries, the Drive’sinfo staff is here to help!

What Happens If I Just Ignore the Potential Problem?

Ignoring a faulty relay or simply putting in any old relay that happens to fit might result in serious difficulties under the hood. If a relay fails to operate properly or if an inappropriate relay is fitted, you run the risk of frying wires and perhaps igniting a fire beneath your hood, which is dangerous. When traveling at 80 mph on the highway, it’s not a nice appearance.

Can I Test Relays Without an Ohmmeter or a Test Light?

No. There are two options if you are confident that there is an issue with a relay but do not have the necessary testing equipment. You may either be cautious and just replace the relay, which is the quickest and most straightforward solution, or you can hire a mechanic to perform the testing and replacement of relays for you.

What If My Vehicle’s Relays Are Hidden or Very Hard to Find?

No. There are two options if you are confident that there is an issue with a relay but do not have the necessary instruments to test for it. To be safe, just replace the relay, which is the quickest and most straightforward solution, or hire a professional to perform the testing and relay replacement for you.

Why Do You Keep Telling Me to Read The Repair Manuals? Isn’tThe DriveSupposed to Be An Authority on These Types of Things?

No. There are two options if you are confident that there is an issue with a relay but do not have the necessary instruments to prove your theory. You may either be cautious and just replace the relay, which is the quickest and most straightforward solution, or you can pay a mechanic to perform the testing and replacement of relays for you.

Do All Vehicles Have Relays?

Given the large number of electrical devices and systems found in modern automobiles, it is reasonable to assume that relays are found in virtually all of them.

How Much Does It Cost To Test A Relay?

The relay itself is the most expensive aspect of the process of testing and replacing relays in your car. It can cost anything from $5 to several hundred dollars to control something using a relay, depending on what it is regulating. Ohmmeters are inexpensive, costing less than $20, and are available in a variety of designs. High-impedance test lights are slightly more expensive than low-impedance test lights, with prices often ranging between $20 and $40. However, investing more money does not always result in a superior product.


  • Best Automotive Multimeter: An Essential Tool for Troubleshooting Electrical Issues Diagnose the electrical faults in your automobile with relative simplicity. Learn how to change your fuel filter right now by reading this article. A blocked fuel filter is just as bad as a clogged artery in terms of performance. Learn How to Repair a Temperature Gauge RIGHT NOW! Your automobile is ‘hot and then chilly,’ to paraphrase Katy Perry’s song. Let’s get this straightened up. Learn how to test a transmission speed sensor by reading this article. It gives critical information to the powertrain computer in your automobile, so check sure it’s in working order. Learn How To Clean Battery Terminals RIGHT NOW! Calcification is not limited to the preservation of dinosaur bones. READ IMMEDIATELY

How to Test a Relay

Article in PDF format Article in PDF format Relays are discrete devices (as opposed to integrated circuits) that are used to allow a low-power logic signal to operate a circuit that requires a significantly larger amount of power to function properly. In addition to isolating the high-power circuit from the lower-power circuit, the relay provides a tiny electromagnetic coil for the logic circuit to control, which helps to safeguard the latter. Testing relays, both coil and solid-state, is something you can learn.

  1. 1 Consult the relay schematic or data sheet for more information. Relays have generally common pin arrangements, although it is preferable to consult the manufacturer’s data sheets to learn more about the number of pins on the relay, if one is provided. Most of the time, this information will be printed on the relay.
  • Information on current and voltage ratings, pin configurations, and other information, which is occasionally accessible in the datasheets, will be helpful in testing and will avoid the majority of errors that occur during the testing process. Testing pins at random without knowing the pin arrangement is feasible, but the results may be unexpected if the relay is faulty. It is possible that this information is printed directly on the body of some relays, depending on their size
  • However, this is not common.
  • 2 Perform a fundamental visual assessment of the relay. Many relays have a translucent plastic casing around the coil and contacts, which makes them easy to see. Damage that can be seen (melting, blackening, etc.) will aid in narrowing down the problem.
  • Most contemporary relays are equipped with an LED that indicates whether or not they are in the active state (ON). If that light is not illuminated and you have control voltage applied to the relay or coil terminals (usually A1 and A2), you may be reasonably certain that the relay is defective.
  • The majority of current relays are equipped with an LED that indicates whether or not they are in the operational mode (ON). It is reasonable to infer that the relay is defective if that light is not illuminated when control voltage is applied to the relay or coil terminals (usually A1 and A2)
  • Prior to undertaking any electrical work, it is recommended that you research your local rules, and if you feel dangerous, you should leave it to the pros. Extra low-voltage work is often exempt from this requirement, although it is still vital to use caution
  1. 1Determine the relay’s coil needs and the size of the coil. The casing of the relay should have the part number of the manufacturer printed on it. Look up the control coil’s voltage and current requirements in the data sheet that applies to the control coil in question. If the relay is large enough, it may also be printed on the casing. 2 Check to see if the control coil is protected by a diode. A diode placed around a pole is frequently used to protect logic equipment from damage caused by noise spikes and other sources of noise. On drawings, the diode will be shown as a triangle with a bar running across one of the triangle’s corners. The bar will be linked to the control coil’s input, also known as the positive connection
  2. And 3 Examine the relay’s contact setup to see whether it is correct. This information will also be accessible from the manufacturer’s data sheet, and in the case of bigger relays, it may be printed on the relay itself. There may be one or more poles on a relay, which is depicted in drawings by a single line switch attached to one of the relay’s pins.
  • A ordinarily open (NO) and a normally closed (NC) contact may be included on each pole of the circuit. These contacts will be depicted on the designs as connections with a pin on the relay. When a relay design is printed, each pole will be shown as either contacting the pin (which indicates an NC contact) or not touching it (which indicates a NO contact).
  1. 4Confirm that the relay contacts are de-energized by testing them. Resistance testing should be carried out between each pole of the relay, and the associated NC and NO contacts for each pole, using a digital multimeter (DMM). All NC connections should have a resistance of 0 ohms to the appropriate pole when tested. It is expected that all NO connections will show infinite resistance to the appropriate pole. 5 Activate the relay by pressing the button. Make use of a power source that is independent of the relay and has the proper rating for the relay coil. If the relay coil is protected by a diode, make sure that the independent voltage source is connected with the right polarity before continuing. When the relay is powered, keep an eye out for a click. Check to see if the relay contacts are in the energized state. Resistance testing should be carried out between each pole of the relay, and the associated NC and NO contacts for each pole, using a digital multimeter (DMM). All NC connections should indicate infinite resistance to the corresponding pole when connected to a power source. All NO connections should have a resistance of 0 ohms to the appropriate pole when tested. Advertisement
  1. 1 Solid-state relays should be checked using an ohmmeter. It is nearly invariably the case that solid-state relays fail when they begin to short. Using an ohmmeter across the normally open (N.O.) terminals of solid-state relays when control power is turned off, verify that they are functioning properly.
  • When control power is provided, the relays should be open, switched to OL, and closed (0.2, the internal resistance of the ohmmeter) until the control power is removed.
  • Use a multimeter in the diode-test mode to check your findings in step two. If you have a multi-meter, you may use it to confirm that the relay is defective by switching it to the diode test mode and testing across A1(+) and A2 (-). The meter will apply a little voltage to the semiconductor to cause it to conduct, and the voltage will be shown on the screen. This will examine the transistor (which is normally NPN) from the base (P) to the emitter
  • And
  • 0 or OL will be displayed on the meter when the relay is defective
  • However, 0.7 for a silicon transistor (which practically all of them are) or 0.5 for a germanium transistor (which are somewhat unusual but not unheard of) will be displayed on the meter when the relay is okay.
  • 3 Maintain the temperature of SSRs. Solid-state relays are simple to diagnose, inexpensive to replace, and, if kept cold, may endure for an extended period of time. New relays are often packaged in DIN rail packages or mounted in block mountings.
  • There is also a specialized sort of relay known as an SCR, which is available in two flavors for heating wires, infrared lamps, and ovens, and is typically used for precise temperature control throughout the manufacturing process. A rapid switch that can flip on and off is essentially what this is
  • Yet, owing to temperature variations, the switch fails frequently.
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  • Question What is the best way to tell if a line relay is operational? Ricardo Mitchell is an American football player who plays for the Los Angeles Lakers. CN Coterie is looking for an electrician/construction professional. In his capacity as CEO of CN Coterie, a fully licensed and insured Lead EPA (Environmental Protection Agency) Certified construction firm based in Manhattan, New York, Ricardo Mitchell has a diverse range of experience. Home renovation, electrical, plumbing, carpentry, cabinetry, and furniture restoration are some of the services offered by CN Coterie. We also specialize in the removal of OATH/ECB (Office of Administrative Trials and Hearings/Environmental Control Board) violations as well as DOB (Department of Building) violations. Ricardo has more than ten years of electrical and construction experience, and his partners have a combined total of more than thirty years of relevant industry knowledge. CN Coterie is looking for an electrician/construction professional. Expert AnswerYou can help wikiHow by unlocking this expert response. Power is supplied to the line relay through the live wire, and a neutral wire and grounding are also supplied to the relay through the grounding wire. On the other end of the spectrum, you have an input and an output that are connected by a coil. As soon as you link the two terminals together, you will hear a clicking sound. If it clicks, this indicates that the coil is in good condition and that your relay is operational. You have a faulty relay if the button does not click.

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Summary of the ArticleXIf you wish to test a coil relay, first make sure there is no power running to it, then use a digital multimeter to measure the resistance between each of the relay’s poles and the contacts for the NC and NO positions. 0 ohms, or zero resistance, should be displayed on all of the NC connections, whereas infinite resistance should be displayed on all of the NO contacts. Afterwards, connect the relay to a power source and listen for a click, after which you should double-check all the poles.

Continue reading to find out how to properly test a solid state relay!

The writers of this page have together authored a page that has been read 762,036 times.

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According to the kind of relay, we will explore several ways for testing a relay in different situations. The first step is to identify the relay you wish to test with the assistance of the graphic shown below. Check for a comparable match relay in this image by looking at it. (Scroll down for a video that explains everything) The first image shows a starting relay in a motorcycle, the second image shows a 5 pin relay used in automobiles, and the third image shows a relay used in electrical circuits.

The following are the most common and general issues identified in starter relays: I Coil (coiling): (conditions- burnt coil, broken connection) ii) Movable contact: (condition- contact has lost its movability and has been carbon covered/rusted as a result of sparks) Diagram of the pinout with the notation: NC stands for ‘normally closed.’ NO: Normally, the door is opened.

How to test a relay with multimeter

(Buzzer mode/Continuity mode, for example) In the case of type 1 and type 3 relays The first approach entails the use of a digital multimeter. Change the mode of the multimeter to the Continuity setting. Step1: Connect the two probes of the multimeter to the coil terminals (C1 and C2) in the manner depicted. If the buzzer continues to sound, your electromagnetic coil is in good working order. The absence of a buzzer signal indicates that your coil is malfunctioning, as described above. The output terminals of the relay must be checked if the buzzer continues to ring.

OR Connect your multimeter probe to the terminal contact (NCCOM).

How to test a relay for type 2:

Continuity of operation mode Step1: The two probes of the multimeter, as well as the coil terminals 85-(C1)86-(C2), must be connected in the manner illustrated. If the buzzer continues to sound, your exciter coil is in good working order (check above images). The output Contact Terminals of the relay must be checked if your buzzer is activated in Step 2. (check above fig). (NOterminals) Using your digital multimeter probe, connect it to the contact terminal (8730). If the buzzer does not sound, this indicates that the contact terminal is in good working order; otherwise, the terminal is defective.

How to test a relay with a multimeter:

(mode of resistance) (common for all type) For starters, change the mode of the multimeter to the Resistor mode. Afterwards, connect the probes of the multimeter (Red and Black) to the coil of the relay like follows:


  • The resistance value for an ortype 1 relay should be in the range of 30 to 150 ohms. The resistance value for a type 2 relay should be in the range of 300 to 900 ohms. In addition, the resistance value for the type 3 relay should be between 20 and 450 ohms.

Along with it, the NO and COM contacts must display 0, which indicates that the circuit is open when noinput is provided.

How to test a relay without multimeter?

(This approach is solely used to determine whether the coil is operational or not.) In order to hear the ‘crisp-click’ sound, you must connect a 12 volt/9 volt/5-volt power supply to the coil (apply voltage according to the rating indicated on it). This shows that your moveable contact is functioning properly and that the relay coil is in excellent condition.

Bonus tips:

  • If your start relay is not working or is only operating intermittently, you should consider replacing it with a new one. This is because the moveable contact on your start relay may have become coated with carbon. Our research has discovered that some motorcycles/mopeds now available on the market suffer starter relay problems more frequently than others
  • Yamaha’s starter relay is at the top of the list.

In short, what is a relay?

It is important to use a relay in circuits where we have a small current but need to drive high current applications because a relay drives high power circuits with the assistance of a low power circuit. Relays are used in circuits where we have a small current but need to drive high current applications.

A relatively popular application for this is to drive the ignition on motorcycles and automobiles. Home Automation Systems are comprised of a huge number of relays that are used to manage various home appliances remotely and through chips.

The symbol of an electrical relay is as shown:

Whenever a current is passed through an electromagnetic coil, it serves as a temporary magnet, drawing the moveable coil into the circuit. This modifies the circuit configuration, which is then used to perform the necessary functions. As a result, when we provide power to a coil, the circuit is closed, and when we withdraw power from the coil, the circuit is disconnected from the terminal. As a result, the circuit gets activated. For the purposes of summarizing, the relay is a ‘ electromagnetic switch ‘ that allows high-current devices to be controlled by a low-current circuit.

What is the best way to test the relay switch?

Exactly how do you check the Yamaha starting relay?

How to test a relay

You will learn how to test a relay in this post. A relay will often be comprised of a coil, a pole terminal, and a collection of contact points. A normally open (N/O) contact is defined as any contact that remains open when the relay is not electrified, and a normally closed (N/C) contact is defined as any contact that remains closed when the relay is not energized, as defined by the relay manufacturer. Testing the relay using a multimeter can be accomplished by following the methods outlined in the next section.

  • Learn how to test a relay by reading this guide! In most cases, a relay will be comprised of three parts: the coil, the pole terminal, and a collection of contact points. A normally open (N/O) contact is defined as any contact that remains open when the relay is not electrified, whereas a usually closed (N/C) contact is defined as any contact that remains closed when the relay is not powered. Testing the relay with a multimeter can be accomplished by following the methods outlined below.

If all of the tests above are affirmative, we may assume that the relay is in good working order. TAKE A LOOK AT THIS: THE WAY RELAYS WORK CHECK OUT THESE TYPES OF RELAYS:

Also interesting

How To Test A Relay At Home (5 Easy Steps)

Several electrical components are integrated into your car, and they all must operate in unison to provide you with a flawless driving experience. These components are in charge of every system in the vehicle, from the headlights to the air conditioning. When anything goes wrong with the electronics, it’s possible that you’re dealing with a malfunctioning relay, which leaves you asking how to check a relay. Because there are multiple relays in the car, you should be familiar with these straightforward procedures.

Even if you are a novice mechanic, you can use our easy procedures to identify the problem and replace it in a short amount of time.

Important Relay Safety

However, while testing automotive relays is very straightforward, there are a number of crucial safety considerations that you should follow. You have the potential to cause significant damage or injury if your actions are not well thought out and executed. The first rule is that you should never replace relays with parts from another vehicle or something you have laying around the house. The use of the improper relay might result in power surges or shorts, which can cause damage to the vehicle’s electronics.

It is possible that wires will melt or burn if the device is dropped or becomes damaged.

Because the relays are powered by electricity, you should avoid using them in areas where there are combustible gases present.

Finally, before dealing with any relay, make sure you have a copy of your repair manual. Although you may be familiar with the fundamentals, it is critical that everything be replaced in accordance with manufacturer standards. 3 Symptoms of a Faulty Main Relay (See Related Article)

Materials Needed to Test a Relay

Testing an automotive relay does not necessitate the use of several tools. In fact, you may already have several of these materials in your garage at home at this very moment.

  • A test light, an Ohmmeter, or a digitalmultimeter are all recommended. Service handbook for the vehicle
  • Relay replacement
  • Jumper wires are used to connect two points.

Ohmmeter or digital multimeter; a test light; Service handbook for the vehicle; relay replacement. Interruptible power supplies; jumper wires

How to Test an Automotive Relay

A few tips on how to test an automobile relay at home are outlined below:

1.Locate the Relay

First and foremost, you must locate the relay in order to test it. The majority of relays can be located behind the dash, however some may be found in the engine bay. The position will be determined by what the relay is in charge of controlling. The wiring diagram for your car can be found in the service handbook for your vehicle if you aren’t sure where to search.

2.Swap the Relay

The quickest and most straightforward method of testing the relay is to switch it with another that is operational. However, by doing so, you run the chance of destroying a perfectly good relay due to an electrical short or other fault that may present. Furthermore, this approach may result in you spending more money than you intended to spend. In the event that you want to take this method, make certain that you clear up the connections and thoroughly check them when the relay is being removed.

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3.Use a Multimeter

You may check the relay’s operation using your multimeter. To measure resistance, set the multimeter to Ohms and connect the leads across the input and output pins of the computer. You’re looking for resistance between 50 and 120 ohms. If the multimeter displays the readings Open or Out of Range, this might indicate a faulty coil winding. In this situation, you’ll need to purchase a new relay. If everything appears to be in working order, you may connect the leads to the switch pins. An open relay will display the letters OL or Open.

4. Add Power

Next, you’ll want to connect a 12-volt battery to the relay and turn it on. When the relay coil closes the connection, you should hear a clicking sound. This is normal. When using diode relays, polarity is critical, but not when using 4-pin relays. The ground terminal of your test light should be connected to the switch terminal. Whether everything is functioning properly, your test light will detect the current and illuminate if everything is in working order. When you take the jumper out of the socket, the light should turn off.

5. Test Switch

With a 12-volt battery, you’ll want to power the relay for the next step. When the relay coil closes the connection, a clicking sound should be heard. Diode relays, on the other hand, do not require polarity to function. The ground terminal and the switch terminal should be crossed by your test light. Whether everything is operating properly, your test light will detect the current and illuminate if everything is in working order. The light should turn off as soon as you remove the jumper.

What is an Automotive Relay?

Relays may be found in almost every modern automobile. Besides that, they are used in a variety of other applications, including aviation and maritime vessels. Relays often allow a lower-amperage circuit to control a higher-amperage circuit, as opposed to the other. The relay operates in the same way as a switch, allowing lower-amperage circuits to be powered at the expense of higher-amperage lines. If you look at the headlights of a car, for example, you will see that a relay is employed. If it wasn’t, you’d have to connect the lights to the switch in your car, which would cause the amperage to surpass the switch’s capability.

Instead, a relay is employed to regulate the system’s operation.

Do you require a maintenance manual?

Take a look at the most suitable alternatives here.

In his more than 10 years as a mechanic, the bulk of which have been spent specializing in sophisticated diagnostics and troubleshooting, he has gained valuable experience. Automotive Diagnostic Technician with certification.

How To Test A Relay With A Multimeter

How to test a relay using a multimeter is what I’m going to show you today in this blog article. The goal of testing a relay is to determine if it is in excellent or terrible working order. One of the most effective methods for accomplishing this is to use a multimeter with an ohmmeter setting and then measure the resistance values.

The First Step Is To Test The Coil of Relay

To find out how much resistance the coil has, consult its datasheet. In addition, the coil’s tolerance value is included in the datasheet for your convenience. Resistance values should be somewhere in the range of 288 to 352 ohms for example if the resistance is 320 Ohms and the tolerance value is 10 percent. Bring your multimeter with you and set it to the ohmmeter setting on the dial. After that, connect the probe leads from the multimeter to both of the ohmmeter’s terminals to complete the circuit.

We are attempting to identify resistance in order to avoid having to deal with polarity.

As long as the resistance falls within the range specified in the datasheet, the device is considered functional.

If, on the other hand, you receive readings that are either extremely high or extremely low, there is an issue with the coil.

The Second Step Is To Test The Terminals of Relay

We’ve now completed our testing of the coil, and it’s time to move on to testing the individual relay terminals. Once again, the most accurate technique to determine resistance is to measure the distance between them. We will be putting the following to the test:

  • NO is for Normally Closed Terminal, NC stands for Normally Open Terminal, and COM stands for Common.

Testing The Normally Closed (NC) Terminal of The Relay

NO is for Normally Closed Terminal, NC stands for Normally Open Terminal, and COM stands for Normally Connected Terminal.

  • NO is for Normally Closed Terminal, NC stands for Normally Open Terminal, and COM stands for Common Terminal.

Testing The Normally Open (NO) Terminal of The Relay

The step by step instructions to test the NO terminal is given below.

  • Make use of the ohmmeter setting on your multimeter. Place one of the multimeter probes on the NO terminal and the other on the COM terminal
  • Then repeat the process. Take note of the opposition
  • If the resistance value is in the range of many M, the NO terminal is in proper operating order.

If you encounter extremely high resistance, to the tune of several M, this indicates that the NO terminal is also operational. This is due to the fact that the impedance is quite high when the NO and COM are not linked.


Hi! My name is Sasmita. I am pursuing my passion for teaching at I hold a Master of Technology in Electronics and Telecommunication Engineering. For anyone interested in learning more about me, please see my ‘About’ page. Thanks for visiting! More information can be found at

How to Test a Relay? Troubleshooting SSR & Coil Relays by DMM

Throughout this essay, we’ll go through ‘ how to test a relay.’ A multitude of factors can lead to the failure of a relay in most cases.

It is therefore critical to test a relay if it has ceased operating before replacing it or discarding it. The use of a multimeter or anohmmeter is required in order to properly test a relay. Before you can test a relay, you must first understand what the relay is made of.

What is a Relay?

A relay is an electromechanical switch that operates on alternating current. It regulates the operation of a circuit by supplying a very little current to activate the coil. The coil creates a magnetic field, which attracts a moveable lever (pole), allowing the switch position to be changed by moving the lever.

  • Relative Post:Different Types Of Relays, Their Construction, and Their Operation Applications

Terminals Of Relay

Related Post:Different Types Of Relays, Their Construction, and Their OperationApplications

  • Two of these are coil input terminals, which are essentially the control input (they activate and deactivate the relay)
  • The other two are output terminals. The feeding input of the high voltage circuit is connected to the common terminal. This input is sent through the relay’s pole (switch) to either the NO or NC terminals depending on the configuration of the relay. It is the terminal of the relay whose connection withcommonterminal stays open when the relay is deactivated that is referred to as the normally opened(NO) terminal. As soon as the relay is activated, it shuts. The normally closed (NC) terminal of a relay is the other terminal of the relay whose connection with the common terminal stays closed until the relay is turned on.

How to Test a Diode Using a DigitalAnalog Multimeter is a related article.

Terminal Identification

The terminals of the relay are typically identified on the protective cover of the relay. If there is no information regarding its terminals, an Ohmmeter can be used to determine what it is and what it is not.

  • Except in a few instances, the coil has a resistance of less than 400ohms. As a result, the coil terminals will be the terminals with a resistance of roughly 300ohms. As a result of the relay being disabled, the NC terminal has nearly zero Ohm resistance in relation to the common terminal. When the relay is turned off, the NO terminal has infinite resistance in relation to the common terminal.

Operation Of Relay

The current will flow from theCommon terminalto theNC terminal when there is no power source connected to the coil input in the deactivated state. Accessed mode: When the coil is powered, the current will only flow from one end of the coil to the other end.

Relay Coil Test:

The current will flow via theCommon terminal to the NC terminal when there is no power source connected to the coil input in deactivated mode. Accessed mode: When the coil is powered, the current will only flow from one end of the circuit to the other end.

  • How to Test a Capacitor Using a Digital-Analog Multimeter is a related post.

Using Multimeter

When testing a relay, there are two modes that may be selected using a multimeter.

Continuity Test Mode

The primary goal of this test is to determine whether or not the coil is still in good working order.

  • Make sure that the multimeter is in the continuity test mode. Placing the probes of the multimeter on the coil terminals is the first step. It is electrically closed (good) if the multimeter beeps (or shows any evidence of continuity)
  • Otherwise, it is not. If the multimeter does not beep, this indicates that the coil is open and broken. It is necessary to replace the relay.

The second technique should be used in the event that your meter lacks a continuity feature or does not exhibit any signs of continuity for any other reason. Unfortunately, if you test a relay using this continuity approach, you will not be able to detect any shorted turns in the coil.

Resistance Mode

Choosing to test a relay using an Ohmmeter requires a little bit of preparation and knowledge on your behalf. It is necessary to know the nominal value of the coil resistance from the datasheet of the coil. You may get its datasheet online by entering the model number, which is normally found on the protective case, into your browser. The resistance of the coil, on the other hand, is usually less than 400 ohms most of the time.

  • Set the Ohmmeter function on the multimeter. Placing the probes on both terminals of the coil is the first step. Make a note of the resistance shown by the multimeter.

If the measured resistance matches the resistance specified in the relay coil’s datasheet, the relay coil is in good working order. If the resistance is extremely low or extremely high, it is most probable that the coil has short turns or has been opened, accordingly. It should be noted that AC coil power relays have a high coil resistance (usually higher than 10kohm). As a result, you must be certain of the sort of relay you are evaluating. How to Check a Transistor Using a Multimeter (DMM+AVO) is a related post.

Using Power Source (Battery)

Recall that you should not use this approach unless you have the requisite technical expertise to operate a power source while also taking the essential safety measures.

  • Recall that you should not use this approach unless you have the requisite technical ability to operate a power source while adhering to safety considerations.

NC (Normally Closed) Terminal Test:

It is required to do this relay test to obtain information on the switching of the relay in order to guarantee that the terminals connect and disengage throughout the coil energizing process.

The NC terminal will stay closed until the relay is turned on.

  • Activate the continuity mode on the multimeter. Place one probe on the relay’s NC terminal and the second probe on the relay’s common terminal. When the coil is de-energized (deactivated), the meter should beep to indicate that the circuit is still active. Now, activate the coil by connecting it to a power source, or you may manually push the lever (armature) by pressing the test button (if it has one) or by using your finger. To silence the continuity indicator (beep), the meter should be turned off.

If the meter does not sound at all, it is most likely because the conductors within have failed. You may also use an Ohmmeter to determine the resistance. If a relay is excellent, its NCterminal resistance is 0 Ohm when it is deactivated and infinite resistance when it is activated.

  • Testing Electrical and Electronic Components and Devices using a Multimeter is a related post.

NO (Normally Open) Terminal Test:

This test verifies that there is a connection between the common terminal and the NO (normally open) terminal (see Figure 1). While the relay is not activated, the NOterminal remains open.

  • Activate the continuity test mode on the multimeter. Placing the probes on NOterminalcommonterminal is a good idea. When the relay is disabled, the meter will not beep or provide any indication of continuity. Now, engage the relay or manually touch the contacts, and the meter should beep to indicate that there is continuity.

A broken relay conductor is indicated by the absence of any continuity reading on the meter. How to Calculate the Value of a Burnt Resistor is another related subject (By three handy Methods)

How to Test a Solid State (SSR) Relay?

This is the most straightforward and accurate method of inspecting and troubleshooting an SSR (Solid State Relay). To put a solid state relay through its paces, follow the diagram and methods outlined below.

  • Assign a control voltage of 9V DC to the input, then connect a switch to the terminals 3 and 4 to operate the device. Connect a 100-watt bulb to the load side of the circuit using 110- or 220-volt alternating current at terminals ‘1’ and ‘2.’ To complete the circuit, the first terminal ‘1’ of the Relay should be linked to the bulb and the alternating current voltage, whilst the second wire from the outlet will be attached to terminal ‘2,’ as indicated in the diagram below. Now, toggle the ‘ON/OFF Switch’ on and off as needed. As long as the light bulb turns on and off as expected, the relay is in good condition
  • Otherwise, the relay has been compromised, and it must be replaced.

Testing ACControlledSSR Relay

When testing an AC-controlled solid state relay, the procedure is the same as described above. However, instead of providing DC control voltage as illustrated in the figure below, you will be required to give AC control voltage. According to the schematic shown below, if the light bulb is ‘ON’ when the switch is closed and ‘OFF’ again when the switch is opened, the bulb is ‘ON.’ You should replace the relay if the condition of the relay is as expected; otherwise, the relay is defective and you should replace it with a new one.

See also:  Ignition Coil? (Correct answer)

Testing Solid State Relay in Diode Test Mode (DMM)

In order to test a solid state relay using a digital multimeter, follow the instructions listed below:

  • As illustrated in the illustration below, turn the multimeter knob to the ‘Diode Test Mode.’ Connect the A 1 (+) and A 2 (-) terminals to the multimeter in the manner depicted in the diagram
  • And 0.7 (in the case of silicon transistors) or 0.3 (in the case of germanium transistors) will be shown on the multimeter if the relay is in excellent working order. Any time a multimeter displays ‘0’ or ‘OL,’ it indicates that the relay has been broken or malfunctioned.

These are some of the most fundamental and straightforward techniques of testing a relay. Any alternative methods or specific techniques for checking and troubleshooting relays should be shared in the comment box below so that our readers can benefit from your knowledge. Posts related to this one:

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  • Electrified Phase or Line Tester – Civil Engineering the operation of the main tester

How do you test a relay fuse with a test light?

Asked in the following category: General The most recent update was on May 9th, 2020. Check for power with thetest lightgrounded, and then connect thetest lightlead to the power side of the battery to check for circuit ground. Step 13 – Using a piece of wire automotive wire (20 to 16 gauge), remove both ends of the wire to expose the copper wire behind the insulation. Simply connect the battery to the therelayterminals that are already attached to the therelaycoil. When you connect the 9 volts battery to the therelaycoil terminals, there will be a click from therelay.

  • Second, what exactly does it imply when a relay clicks on and off?
  • If the computer fails, resistance in the ground wire for the control side of the therelay, or a high resistance in the power supply to the control side of therelay are all possible causes of the problem.
  • A jumper wire, a voltmeter, an ohmmeter, or a testlight can all be used to inspect the relay.
  • A defective relay coil is indicated by the absence of electricity.
  • What causes a relay to malfunction?

Accidents and malfunctioning UUTs can cause relay failures even in low-level signal applications, and inrush currents and voltage spikes induced by hot-switching capacitive loads, as well as voltage spikes caused by hot-switching inductive loads, can accelerate relay aging.

How to Test a Fuel Pump Relay and Other Automotive Relays

Dan Ferrell is a writer who specializes in do-it-yourself auto maintenance and repair. Simple techniques may be used to test an automobile relay, which is courtesy of Alex Roberts on Flickr.A fuel pump relay can fail in various ways.Photo courtesy of Alex Roberts on FlickrA fuel pump relay can fail in several ways. Despite the fact that a failed fuel pump relay — or any other automotive relay — can cause trouble from time to time, many car owners choose to simply replace a suspect relay and end up wasting money and time in the process.

The following is the table of contents.

Table of Contents

I.What is an Automotive Relay and how does it work? II.How It WorksIII.How to Find the Fuel Pump RelayIV.How to Test a Fuel Pump Relay or Other Automotive Relays in the Fastest Possible Time When testing the fuel pump relay, use a special relay tester or a digital multimeter. V. When testing the fuel pump relay, use a digital multimeter.

I. What Is an Automotive Relay?

The first question to ask is: What is an Automotive Relay. 2.How It Works3.How to Find the Fuel Pump Relay4.How to Test a Fuel Pump Relay or Other Automotive Relays in the shortest amount of time. When testing the fuel pump relay, you can use a special relay tester or a digital multimeter.

II. How It Works

Think of a relay in the same way you would think of a standard switch, such as the one you use at home to turn on and off the lights in a room. Similarly, a relay operates in the same way, except that instead of reaching into the relay and flipping on the internal switch directly, you energize a control circuit that connects to a coil inside the relay — for example, when you turn the ignition switch to start the engine, you energize the fuel pump relay. For example, when the coil generates an electromagnetic field, it closes a pair of metal contacts within the relay, which are connected to a regulated circuit that triggers a load — such as an electric fuel pump — to activate it.

It came out to be a convenient setup in electrical circuits, as it turned out to be.

A relay can be placed in a strategic location to reduce the amount of thicker gauge wire required for high current circuits, as well as the costs associated with it.

Testing Relays

In the event that you haven’t already done so, you’ll need to identify the fuel pump relay.

Search for problems inside the power center beneath the hood (a box with relays), along the firewall, or in the fuse box(es) under the dashboard and on the sides of the vehicle.

Read More from AxleAddict

On the back of the lid of these boxes, you may discover marks indicating which relays are included within them, as well as a brief explanation of each relay. Depending on the vehicle type, the fuel pump relay may be located on its own someplace beneath the dashboard or under the hood. You should consult the vehicle maintenance handbook for your specific automobile if this is the case. In addition to buying it online, most auto parts retailers provide aftermarket repair manuals for a variety of vehicle makes and models.

Choose the one that is most convenient for you.

IV. The Fastest Way to Test a Fuel Pump Relay or Other Automotive Relays

The quickest and most straightforward method of testing a suspicious fuel pump relay — or any other automobile relay — is to simply exchange the problem relay with a good one that works. It’s possible that you’ll locate another relay in your automobile that has the same layout as your gasoline pump relay, with the same arrangement and number of connections. Another option is to borrow a relay from a relative’s or friend’s automobile. Simply ensure that the other relay has the same setup as the first.

If this is the case, a new relay should be installed.

V. Using a Special Relay Tester

The use of an arelay tester is another method of checking your fuel pump relay. Testing equipment to assist you in troubleshooting the most common automotive relays may be found on the market, as well as more advanced testing equipment to assist you in troubleshooting relays with a variety of configurations. The fact that you do not require schematics or wiring diagrams makes the troubleshooting process more faster and more efficient. Simply follow the on-screen instructions that come with the device.

The image is courtesy of Waifer X.

VI. Using a Digital Multimeter to Test the Fuel Pump Relay

However, it is more than likely that you will not be testing relays on a regular basis, and as a result, you will not need to purchase a relay tester. You may still do the same function using a digital multimeter, if you like. If you don’t already own a digital multimeter, you should invest in one. In various situations, such as automotive and house troubleshooting, they are quite useful. Your local electronic parts store, hardware store, department store, or internet retailer may have a helpful, high-quality, and reasonably priced digital multimeter available.

1. Visual Inspection

  • Pull the relay out of the socket and physically check the terminals and socket for signs of corrosion and overheating before proceeding with the testing. Corrosion limits appropriate current flow, and overheating signals that there is a problem with the relay or the circuits it is linked to. If required, do a circuit check. Electrical contact cleaner should be used to clean corroded terminals and sockets.

2. Identifying the Fuel Pump Relay Terminals

You must now determine which pins or terminals are connected to the control circuit and which are connected to the load or regulated — also known as power — circuit. When you turn on an automobile relay, the control circuit is the one that is activated by either you or the computer. The load or power circuit is the circuit that contains the load or accessory that has been activated or is about to be triggered (fuel pump, radiator fan, headlights, horn). Many automotive relays include a schematic imprinted on the casing itself to identify each pin or terminal with a number, which may be helpful for troubleshooting.

The numbers 85 and 86 are used for the terminals linked to the control circuit, while the numbers 87 and 30 are used for the terminals connected to the load or power circuit, according to manufacturer standards.

They may, however, differ depending on the arrangement.

Relays with no numbers or diagrams to identify the terminals can still be found on the market.

The terminals of the power circuit are connected to the thick wires. The control circuit terminals are connected by means of the thin wires.

Common Relay Terminal Designations

Common Relay
Control circuit 85 86
Power circuit 87 30
(normally closed) 30 87a
Micro Relay
Control circuit 1 3
Power circuit 2 4

3. Checking for Continuity

It is necessary to verify for continuity between the power circuit terminals once you have identified the terminals.

  • Set your digital multimeter to the lowest range on the Ohms scale, or to the ‘continuity’ setting on your computer. Then, connect one of the leads to one of the power circuit pins and the other lead to the other power terminal to complete the circuit. It is expected that your meter would read infinite (OL, open load) resistance. Otherwise, you should not hear a beeping sound if you are using the continuity setting
  • If you detect 0 ohms or any resistance number in the hundredths or thousandths of an ohm, instead of infinity, or if you hear a beeping sound, this indicates that the power pins of your relay have shorted out. Replace the relay with a new one.

When the power circuit is not activated, the relay switch for the power circuit is frequently in the typically open position, as is the case with a fuel pump relay. Because some automotive relay power switches come normally closed and should open when energized — typically, these terminals are labeled 30 and 87a — when testing another automotive relay, make sure to check the diagram on the relay or the wiring diagram in your car repair manual before starting the test. As previously stated, while testing for continuity, your meter should indicate zero Ohms or make a beeping sound, if it is functioning properly.

4. Checking That Your Relay Works Properly

  • As soon since feasible, attach a jumper wire (preferably one that has been fused, as these are available at most auto parts stores) from the battery positive (+) connection to one of the control-circuit terminals of the relay. Connect another jumper wire from the negative (-) battery terminal to the other control-circuit terminal of the relay
  • This will complete the circuit. The contacts (switch) in the power circuit of the relay should generate a clicking sound when they close, which you should hear as you attach the second jumper wire to the relay and turn it on. You should replace the jumper wire connections on your relay if you don’t have one. As a result, connect the jumper wire from the positive terminal of the battery to the other terminal on the control circuit, and repeat this procedure with the negative terminal, just in case the control circuit has an issue with crucial polarity. If you are still unable to hear a click, it is likely that the control circuit link in the relay failed. Continue with the rest of the test, though, to ensure that there isn’t an issue with the relay. Continue to connect the jumper wires and check for continuity between the power terminals in the same manner as you did previously. Now, your meter should display 0 or near to zero resistance (in the hundredths or thousandths of a resistance), or it should beep to indicate that continuity exists between the two terminals (see figure). If this is the case, your relay is functioning properly (but remember that if your relay switch is in the typically closed position, your meter should read infinite resistance or make no beeping sound at this moment)
  • Instead of this, replace the relay if your meter indicates infinite resistance or if you hear no beeping sound at all
  • Check for faulty wires, corrosion on the terminals and connections, detached wires (opens), and short circuiting around the control and power circuits if your tests show that your relay is in good working order. A failure in any of your circuits will be caused by any of the factors listed above.

Once you’ve learned how to test a gasoline pump relay, you’ll be able to test most other automobile relays with relative ease. However, you may get relays with three, five, or even six terminals on the market. On three-terminal relays, the casing itself can be used as a ground connection because of the design. Others with five or six terminals control more than one power circuit, and certain internal switches are generally opened while others are normally closed, depending on the configuration.

Then, proceed with your testing as stated above.

Content is provided solely for informative and entertainment reasons and should not be relied upon as a substitute for personal counsel or professional guidance in commercial, financial, legal, or technical problems, unless otherwise specified.


When I turn on the ignition, the gasoline does not come on. Is this normal? What may be the source of the problem? Answer:If the engine turns over but does not start, the fuel pump may be faulty. When you turn the key on and pressurize the gasoline line, you will usually be able to hear it. If this is not the case, the pump should be checked. Question:My relay is in fine working order, but the car still won’t start. We removed the fuel pump relay and inserted a bobby pin into the circuits, and the car started right away.

As a result, if electricity is passing through the relay, it is necessary to determine whether or not voltage is reaching the fuel pump.

What is the reading on a multimeter that a fuel pump relay is meant to give?

As a precaution, if you are testing the relay while the pump is operating, consult your vehicle repair manual to identify the wires and specifications to use.

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