In most cases, a blower motor resistor fails due to corrosion or overheating. Sometimes, the mechanical resistance to the motor rotation causes an excessive electric current that can overheat and prematurely damage the blower motor resistor.
What causes heater resistors to burn out?
Trent, one of the biggest reasons for blower motor resistors to have shorten life is actually because of faulty blower motor drawing too many amps, some times melting wires/plugs, heating up resistors shortening their life.
Why does my blower motor relay keep blowing?
Blown fuses If the blower motor relay develops any sort of problem that hinders its ability to properly limit and distribute power, it may cause the blower motor fuse to blow. Any sort of electrical spikes or excessive current from a bad relay will blow the fuse and cut power in order to protect the system.
Can a blower motor resistor be intermittent?
Reduced airflow is when the blower motor is trying to move air through the vents but the resistor isn’t sending enough power to move the air with much pressure. Depending on how much resistor is still functioning, the reduced airflow could be an intermittent problem.
Will blower motor work if resistor is bad?
No air comes out of the vents There are instances where a bad resistor will prevent the current from reaching the blower motor altogether. Without any power, the motor won’t run. As a result, the blower fan stays still and silent, and no air blows out of the vents.
Can a blower motor resistor be bypassed?
Blower resistors are made of several resistors with different resistances. In the highest speed state, the blower resistor is bypassed completely and the fan is connected directly to the car’s battery, which allows maximum current through the motor.
What causes a resistor to go bad?
A fixed composition resistor normally fails in an open configuration when overheated or overly stressed due to shock or vibration. Excessive humidity may cause an increase in resistance. A variable composition resistor may wear after extensive use, and worn away particles may cause high resistance short circuits.
Why will a blower run on the on position and not on auto?
Other Blower Fan Won’t Run Problems The fan will run and blow warm air but only in FAN or FAN ON mode – delivering heat – but NOT in AUTO mode. This is a bad temperature sensor in the unit; replace the fan limit controller.
How do I know if my blower relay is bad?
If you have a faulty blower motor, you may experience low airflow from the vents, even when the fan is on high. There will be no air coming from the vents if your fan isn’t working due to a bad blower motor resistor.
How do you test a blower motor resistor?
Place one lead of the Ohmmeter on terminal 1 of the resistor. Place the other lead on terminal 2 and check against specifications. If this circuit is open, showing infinity on the Ohmmeter, the blower resistor must be replaced. Move the lead from terminal 2 to terminal 3 and check this reading against specifications.
Why does my blower motor work sometimes?
When a blower resistor fails, the highest fan speed usually is the only one that still works because it essentially bypasses the resistor and receives the maximum amount of voltage. When the resistor is working, it reduces the amount of voltage going to the lower fan speeds so the fan runs slower.
How do you fix a blower motor resistor?
How to Replace a Blower Motor Resistor
- Step 1: Remove the glove box door, if necessary.
- Step 2: Disconnect the wiring harness and remove screws.
- Step 3: Remove and replace the blower motor resistor.
- Step 4: Tighten screws and reattach wiring harness.
- Step 5: Reinstall the glove box door.
What makes a blower motor go bad?
Blower motor breakdown can be the result of anything from old age to failed bearings, high amp draw, electrical failure in the windings, dirt accumulation, and more. “The most common cause is dirt accumulation due to lack of maintenance,” said Tom Beaulieu, president of Bay Area Services Inc.
How do you know if you have a bad blower motor resistor?
If the airflow from the vents is weak… If you try to increase the air pressure and you feel no difference in the pressure blowing, then your blower motor resistor may be failing. A damaged blower motor resistor will work on one fan speed which may not be enough to keep the inside of your car cool or warm enough.
Is there a fuse for the blower motor?
Many vehicles have two fuses for the blower motor, one in the interior fuse block and the other under the hood. The blower motor is usually under the dashboard on the passenger side.
Blower motor resistor keeps failing
Go to your
local Firestone Complete Auto Care if your car’s air conditioning blows cold first, then hot. When it comes to diagnosing the problem with your automobile air conditioner, an A/C performance check is the most straightforward method. Make an appointment online or visit your local location to get started right now.
What causes a blower motor resistor to fail
The fundamental essence of resistors is to obstruct the passage of electricity, similar to the function of a flow restrictor in a pipe. Resistors, on the other hand, create heat as a result of their ability to reduce current flow. Over time, the heat generated by the resistor might lead the resistor to fail on its own. Automobile manufacturers place the blower motor resistor in the heater duct so that it is exposed to cooling airflow, which reduces the probability of failure.
Worn blower motor causes repeat blower motor resistor failure
Resistors, like a flow restrictor in a pipe, are designed to prevent the passage of electricity by their very nature. Resistors, on the other hand, create heat as a byproduct of limiting current flow. As a result of the heat, the resistor may eventually fail on its own accord. The blower motor resistor is located in the heater duct so that it is exposed to cooling airflow, which reduces the probability of failure.
High resistance in the electrical connector can cause repeat blower motor failure
Actually, corrosion or poor contact in the blower motor resistor connection is the cause of this problem. An overheating problem might also be caused by a faulty blower motor resistor. In certain instances, the heat is so intense that the connection is completely melted. This is a regular occurrence on late-model General Motors automobiles. It is not recommended that you attempt to repair a melted connection. Purchase an improved pigtail and splice it into the harness, along with a new blower motor resistor, to complete the installation process.
Water, leaves and debris in the airflow can cause blower motor resistor failure
The HVAC systems in automobiles are designed to minimize the likelihood of debris entering the system during operation. They are not, however, always successful. If water spray enters the system, it has the potential to quench the hot resistor wires, causing them to break and short out. If you detect a loss of one blower motor speed or the loss of all blower motor speeds shortly after driving through rain, the blower motor resistor may have been damaged by water. Rick Muscoplat has a new year’s resolution.
Blower motor, resistor: how it works, symptoms, problems, testing
The most recent update was on August 1, 2021. In automobiles, a blower motor is a type of motor that drives the fan in the vehicle’s heating and air conditioning system. It is usually found inside the dash, on the opposite side of the steering wheel, or inside the engine compartment, on the firewall, depending on the vehicle. It is the blower motor resistor, also known as the blower motor control module, that is in charge of controlling the blower motor’s rotational speed. What exactly is the distinction?
It is used in automobiles if the blower motor has just four or five fixed speeds, as seen on the left side of this picture.
As seen in the photograph, an electronic blower motor control module is installed in cars equipped with an automated temperature control system and vehicles in which the blower speed may be changed gradually.
This is done in order to allow air to circulate around the resistor or control module, allowing it to cool down. Occasionally, in earlier vehicles, a blower motor resistor was mounted on the firewall, with access provided from underneath the hood.
Blower motor resistor / control module problems
In many automobiles, problems with the blower motor resistor are prevalent. Generally speaking, the most typical sign of a failed blower motor resistor is that the heater fan only operates at the maximum speed level (4 or 5) and does not operate at lower speed settings. In some automobiles, a faulty blower motor resistor can cause the heater fan to stop functioning altogether in rare instances. The majority of the time, a blower motor resistor fails as a result of corrosion or overheating. Mechanical resistance to motor rotation can occasionally result in an excessive electric current flowing through the motor, causing it to overheat and prematurely destroy the blower motor resistor.
Problems with a blower motor control module are less common, but they occur for the same reasons: corrosion or overheating when the motor is blocked or shorted, for example.
Occasionally, a faulty blower control module or processor can cause the blower motor to continue operating even after the ignition is turned off in some vehicles (e.g., older General Motors trucks).
How is the blower motor resistor diagnosed?
The rust in this Ford blower motor resistor has caused it to fail. Diagnostic procedures differ from one another. A visual check of the resistor will frequently uncover the source of the problem. Examples include the failure of the blower motor resistor in a Ford Escape due to corrosion, as shown in this photograph of the vehicle. The resistance between the resistor’s terminals must be tested and compared to the manufacturer’s requirements if there is no visible damage to the resistor. If the resistance is not within specifications, the resistor will need to be changed.
- According to the service handbook, the resistance should be between 4-5 ohms.
- In our scenario, the ohmmeter indicates that the resistor has failed, which signifies that the resistor has failed.
- This indicates that after replacing the blower motor resistor, you should check to see if the blower motor is running smoothly and without making any noise.
- This was a prevalent problem in earlier Chrysler and Dodge minivans, for example.
- When a blower motor is worn out, it might make a loud screeching noise occasionally while operating, which is one of the signs of the problem.
How to test the blower motor?
If the blower motor does not function at all, the blower motor itself must be inspected first to determine the cause of the problem. Most of the time, this is accomplished by monitoring the voltage at the blower motor connector when the blower is switched on. There should be a voltage present at the motor (at least 4-6 Volts at low speed and 12 Volts at high speed), but the motor should not be running because it is defective or stuck. Checking the voltage at the blower motor is a good idea. It is a defective motor if there is voltage at the motor (at least 4-6 Volts at low speed and 12 Volts at high speed), yet it does not operate while there is voltage present.
- This occurs often in a large number of automobiles.
- This includes testing the circuit starting at the fuse.
- A faulty blower motor will necessitate the replacement of the unit.
- This is a relatively simple task in many automobiles; the blower motor is placed under the glove box and is held in place by three to four screws.
If you want a proper diagnostic method, we have provided various links to websites where you may obtain a service manual for your vehicle for a small membership charge. Check out this article by scrolling down the page.
How is the blower motor control module tested?
First and foremost, if the blower motor does not function at all, the blower motor must be examined. Most of the time, this is accomplished by monitoring the voltage at the blower motor connector when the blower is activated. There should be a voltage present at the motor (at least 4-6 Volts at low speed and 12 Volts at high speed), but the motor should not be running because it is damaged or stuck. The voltage at the blower motor is being checked. Even though the motor has electricity (at least 4-6 Volts at low speed and 12V at high speed), if the motor does not operate, the motor is faulty and must be replaced.
- This occurs frequently in a large number of automobiles, including mine.
- Take a look at this article: how to check the fuses in a car for more information.
- Depending on the vehicle, the blower motor replacement might cost anywhere from $320 to $650.
- Others, such as the Mazda 5, may have it hidden under the dash, making replacement more challenging.
- Scroll down the page to see this post.
Your neighborhood mechanic or any small repair business should be able to determine the source of the malfunction. Of course, scheduling an appointment with your dealer is the most expedient option. A large number of dealers have the component in stock. The cost of replacing the blower motor resistor or control module is not prohibitively high. A coworker of ours, for example, had an issue with his 2011 Ford Escape, which had a fan that only operated at speed 4. In the end, he spent $50 for the diagnosis and $112 for the resistor replacement at a local Ford shop.
The blower motor resistor is found on top of the HVAC unit, behind the glove box, in the Ford Escape / Mazda Tribute from 2008 to 2011 model years.
It’s kept in place by two screws and is simple to swap out.
The blower motor resistor is likewise positioned beneath the glove box in the Ford F150, however it is mounted on the right side of the plastic air duct in the model years 2008 to 2011.
It was written by the author of this site on his experience changing the blower motor resistor in a Jeep Liberty. It is possible that the blower motor resistor is located on the firewall of some vintage automobiles and trucks, and that it is only accessible from below the hood.
How the blower motor resistor works
Diagram of a typical blower resistor This figure illustrates the connection of the blower motor resistor in a common automobile. In this vehicle, the resistor is bypassed when the fan speed is set to the maximum ‘4’ level, and the blower motor is driven directly by the fan switch. That’s why in some automobiles, the blower motor may still run in the ‘High’ speed setting if the resistor is defective. The fan switch is set to speed ‘1’ in this figure, and the blower motor current is lowered by three resistors (R2 + R3 + R4) that are connected in series with the fan motor.
In the option ‘2,’ there are two resistors linked in series, however in the setting ‘3,’ there is just one resistor connected in parallel.
When numerous resistors are linked in series, the overall resistance increases and becomes equal to the sum of the individual resistances in each series connection.
Why does my blower motor resistor keeps melting?
Trent, one of the most common causes of shortened life in blower motor resistors is a malfunctioning blower motor that draws too many amps, melting wires and plugs in certain cases, and heating up resistors, causing them to fail sooner than they should have. After that, they purchase an aftermarket blower motor, which continues to burn. In many automobiles, problems with the blower motor resistor are prevalent. Blower motor resistor failure is most commonly shown when the heater fan only operates at the highest speed setting (4 or 5) and does not operate at lower speeds.
- Is it also intended for the blower motor resistor to become hot during operation?
- Although the majority of people are unaware of this, defrosting the windshield at a low or medium fan speed is more efficient due to the heat generated by the resistor.
- In light of this, how can I determine whether or not my blower motor resistor is bad?
- What to Look for When Your Heater Blower Motor Resistor is Bad or Failing
- The blower motor is locked at a single speed. On some settings, the blower motor does not operate. There is no air coming from the vehicle’s vents.
What is the best way to tell whether a resistor is bad? Set the ‘ohms’ setting on a digital multimeter. Decide on an ohms range that is equal to or more than the value of the resistor that will be evaluated. Put your finger on one of the red leads from the meter and the other finger on the black lead from the meter. Because resistors do not have a polarity, it makes no difference which side of the resistor receives the red or black connection.
How can you tell if the blower motor resistor is bad?
Asked in the following category: General The most recent update was made on May 10th, 2020. Blower motor resistor failure is most frequently manifested by the heating fan only operating at the maximum speed setting (4 or 5) and failing to operate at lower speeds.
In some vehicles, a faulty blower motor resistor might cause the heating fan to cease functioning altogether. What to Look for When Your Heater Blower Motor Is Bad or Failing
- The airflow from the vents is insufficient. Low airflow from the vents is one of the first signs of a potential problem with the vehicle’s heater blower motor
- The fan only blows at particular speeds is another. Another indicator of a faulty or failed heater blower motor is a motor that only operates at specific speeds
- No air coming from the vents
- And a motor that only operates at certain speeds.
Furthermore, how does one go about testing a blower motor? How to Perform a Blower Motor Check
- To check for a blown fuse, use a voltmeter or an ohmmeter to measure the resistance. If you come across one, replace it. Start the automobile and check to see whether the blower motor is operational. Examine the circuit for any loose connections if the fuse blows again. If the circuits are in good working order but the blower motor continues to blow fuses, the blower motor should be replaced.
Is it possible to bypass a blower motor resistor in light of this? The blower resistor is wired in series with the blower fan to create a vacuum. When the blower motor is in the off position, it is removed from the power source. In the highest speed mode, the blower resistors are totally bypassed, and the fan is linked directly to the car’s battery, allowing the motor to draw the greatest amount of electricity possible. Is there a fuse for the motor that blows air? The blower motor is driven by a relay, which is similar to a fuse in appearance.
The position of your blower motor fuse may differ from vehicle to vehicle, despite the fact that it is simple to change.
Blower Motor Resistor Keeps Failing
Thank you for your responses! Perhaps I should try replacing the blower motor and resistor to see if it makes a difference. TSB 04-15-3 also recommends replacing both and adding something called a rain-hat extension seal to the cowl near the passenger windshield wiper, as well as some silicone rubber to prevent water from getting into the blower, according to my research. Here is TSB 04-15-3 in its entirety. Sorry, but the statistics it references to did not appear when I copied and pasted it into this document.
Blower motor for central air conditioning that is erratic or inoperative 09/04/2004 TSB 04-15-308 09/04/2004 BLOWER MOTOR AND/OR RESISTOR FAILURE IN VEHICLES BUILT FROM 5/1/2001 TO 12/15/2003 IF THERE IS WATER IN THE BLOWER CASE FORD:2001-2004 TaurusMERCURY:2001-2004 Sable To bring the vehicle model years and construction dates up to date, this page supersedes TSB 03-15-06, which was published on June 15, 2006.
- ISSUES There have been reports of water in the blower case or on the passenger side floor in some cars constructed between 5/1/2001 and 12/15/2003, as well as an inoperable temperature control blower motor, a motor that only runs at high speed, and/or a blower motor resistor failing in some.
- If there is evidence of water/corrosion, inspect and replace the blower motor and/or the blower motor resistor as needed.
- SERVICE OPERATING PROCEDURE 1.
- Examine the area for signs of water or corrosion.
- Visually check for a properly installed rubber seal on the vent screen, which should be completely flush with the windshield.
Pollen filter removal and inspection of the cabin filter to ensure that it is properly placed are both required.
Ensure that the rain-hat base is secure and well-sealed to the body by visually inspecting it.
Remove the tape and fill the tiny hole with Clear Silicone Rubber TA-32 in the manner shown (Figure 2).
Attach the Rain-Hat Extension Seal or Shed Lip Seal 4F1Z-54022A54-AA to the outboard edge of the rain-hat using the hat extension seal or shed lip seal 4F1Z-54022A54-AA (see Figure 2 for installation).
If the cover is not properly snapped in place, the cover will feel loose and will need to be tightened with a screwdriver.
Block of Parts WARRANTY STATUS: Eligible for coverage under the terms of the New Vehicle Limited Warranty.
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Blower Motor Resistor Operation
The blower motor resistor is in charge of regulating the blower motor’s rotational speed and voltage. It used to be possible to accomplish this simply adjusting the voltage supplied to the blower motor. Recent applications have replaced the blower motor resistor with a solid state module that delivers a variable signal to the blower motor to operate the fan. The typical blower motor resistor is connected to ground and wired in series with the blower motor assembly in order to provide maximum efficiency.
This regulates the amount of current that flows through the blower motor.
In turn, the change in resistance controls the current that flows through the blower motor, which, in turn, regulates the speed at which the blower motor rotates.
In this way, the maximum current may be sent to the blower motor, and the maximum speed can be achieved.
Typical Blower Motor and Resistor Wiring
Reminder: Before you begin testing, make sure you have the wiring diagrams and system functioning for the blower motor and resistor that are specific to the vehicle application. Testing Suggestions
- To determine the particular testing methodologies and resistance values for ohm testing the resistor itself, see the service information. Check for electricity to the blower motor. Check the primary ground connection between the switch and the resistor. Check to ensure that the ground is connected to each pin of the resistor and each pin of the switch and blower motor. Check that power gets through the switch and to the resistor terminals when the resistor is disconnected
- Otherwise, replace the resistor.
Power Tip: When the blower motor resistor is in action, it generates a lot of heat. For this reason, the resistors are placed in the direction of the blower motor airflow, which cools them while also providing cooling to the motor. In most cases, if the blower motor is driven with the resistor assembly removed from its original place, it will result in the blower motor resistor failing. Excessive blower motor amperage caused by a malfunctioning blower motor or a limited cabin air filter should also be evaluated, and if necessary, replaced in order to avoid recurrent failures in the future.
- The vast majority of manufacturers have transitioned away from basic resistor circuits and toward electronic control modules and solid state controllers.
- It is usually advised that you consult the service manual for the individual car you are working on.
- Excessive current can be generated by worn-out blower motors.
- It is anticipated that the new blower motor control assembly would fail as a result of the increased current.
- It is necessary to double-check information on specific vehicle uses.
- It occurs when the blower motor control assembly, which is now installed or is about to be installed, is activated before it has been entirely mounted in its right placement on the blower motor.
This failure may occur immediately or it may result in a return at a later period. It is critical that there be sufficient airflow within the vehicle in order to prevent the blower motor control component from overheating. The cabin air filter should be checked on a regular basis as well.
Blower motor resistor keeps burning?
After replacing the majority of the components, the resistor continues to heat up. I’d search for melted insulation or melted connectors in all of the cabling that connects the fan motor, resistor pack, and fan speed switch, as well as any other problems. When the fan motor in my 1997 Jeep TJ failed, it drew so much current that it ripped out a lot of the wiring and connectors in the process. It had melted the wiring insulation, there was exposed bare wire, and one of the connections had melted as well.
I’d search for melted insulation or melted connectors in all of the cabling that connects the fan motor, resistor pack, and fan speed switch, as well as any other problems.
It had melted the wiring insulation, there was exposed bare wire, and one of the connections had melted as well.
I didn’t see the point in starting a new thread.
I tested the resistor and found it to be in good working order.
I spoke with the former owner, who confirmed that this had occurred previously.
Then I noticed a scent of heat, and the resistor pack had stopped working.
This time, I was paying attention to the resistance and saw that the coils in the pack were burning red at any of the three speeds.
A wonderful price was found on a new blower motor, which I purchased and installed, but I’m still experiencing the same problem.
My previous electrical experience was in a physics lab, which was oh so many years ago, similar to that of the original poster.
Problem: The blower motor only has a fourth speed.
So far, the following steps have been taken: The switch has been replaced.
A new resistor pack has been released.
New Issue: Resistor coils flash for a short period of time before failing at speeds 1-3.