Normal Car AC manifold gauge readings? (TOP 5 Tips)

What are normal AC gauge pressures when the system is running? Generally speaking, you want around 27-psi on the low side and 200 on the high side.

  • * Normal readings on high and low side with AC OFF (static pressure) – Depends on outside temperature, but normally is between 80-105 PSI * Normal low side reading with AC on high-speed and MAX engine at 800-1000 RPM’s – Ranges from 25-35 PSI – Note that on many Chrysler products a normal reading on the low side may be 15-25 PSI

What is normal pressure for car AC?

The low-side should be near 30 PSI at 90 degrees Fahrenheit or less. Pressure that is too much lower or higher shows there is a problem. On a properly working system, high-side pressure will be about twice the ambient temperature, plus 50 PSI.

What pressure should AC gauges read?

If you think that you have an issue with your A/C system but you are not sure which component is causing the malfunction it is a good idea to hook your compressor up to a pressure gauge. An A/C System that is working properly should have 150 PSI on the high side and 30 PSI on the low side.

What should AC gauges read R22?

R22 gauge pressure is 10.9 bar or 158.2 psi. High side pressure typically varies by equipment and metering controls. Low pressure or suction side typically varies by equipment. Low-pressure refrigerant turns on the carrier HVACR at 50 psi (R22 pressure at 30 degrees) and closes at 100 psi (R22 pressure at 85 degrees).

What is manifold gauge?

A manifold gauge is a pressure-checking system. When used as a service tool, a manifold gauge can be used to release moisture and sludge, and remove contaminated refrigerants from the system.

What happens when car AC is overcharged?

Overcharged car ac can lead to some pretty serious repairs down the road if left alone. Additionally this can actually cause your whole ac system to fail as it can also damage the ac condenser. While this is uncommon it does happen. The condenser takes the refrigerant in it’s gas form and pulls the heat away from it.

How do I know if my car AC compressor is bad?

What Are the Signs and Symptoms of a Bad A/C Compressor?

  1. A Lack of Hot Air Being Released Outside.
  2. Loud or Strange Noises From the Unit.
  3. Failure of the Compressor to Turn On.
  4. Circuit Breaker Tripping.
  5. Leaks Around the Air Conditioning Unit.
  6. Warm Air Instead of Cool Air Being Delivered to the House.
  7. Reduced Airflow.

How much 134a does a car take?

Most newer passenger car A/C systems do not hold much refrigerant (only 14 to 28 oz.), so you don’t want to add too much if the system is low. One can of R-134a typically holds 12 oz. of refrigerant. 11.

AC pressure gauge readings

Employ of a low-pressure gauge on a recharge kit is insufficient for diagnosing your car’s air conditioning since you are only observing pressure on the suction or low side of the entire system when you use this method. Unfortunately, there is insufficient information to diagnose a problem. It’s the equivalent of attempting to diagnose your entire health based on only half of your blood pressure measurement. Look, I understand your want to diagnose and repair your car’s air conditioning problem without purchasing any gear, but you may seriously damage your car’s air conditioning system if you overcharge or undercharge the system.

To truly diagnose and repair your air conditioning system on your own, you will want an AC manifold gauge set with hoses as well as a variety of other tools and supplies.

Start your AC pressure readings diagnostic by measuring the system’s STATIC pressure

The pressure that exists while the system is at rest is known as static pressure (compressor off for at least 30-mins). Assemble the hoses and gauges, then connect them to the high and low side ports of your air conditioner. 1. After turning off the engine for at least 30 minutes, check the low and high pressure gauges to ensure they are working properly. They should be the same since, after the compressor is turned off, the high and low side pressures will be equalized. Because it takes time for the pressure to equalize, you must wait 30 minutes before checking static pressure.

Using a THERMOMETER, check the temperature of the surrounding air in the car and under the hood (do not use weather service temperatures).

Comparison of pressure data with the pressure-temperature chart is done in step 3.

R-134a Static Temperature pressure chart

WARNING: The temperature beneath the hood of the car, NOT the temperature reported by the WEATHER SERVICE, is the ambient temperature.

What static pressures actually means

When the static pressure value is low, it indicates that the system is low on refrigerant.

Static pressure only tells you two things

They only tell you two things if the low and high side gauges read the same pressures and if the readings correlate to the pressures and temperatures displayed on the chart above:

  1. The system isn’t wholly devoid of information
  2. The pressure in the system is high enough to allow the compressor clutch to be engaged.

If the static pressure is less than 27 psi and the ambient temperature is greater than 33°, the air conditioning system will not activate the compressor and you will not receive any cooling.

If the gauges aren’t the same during a static pressure test

During a static pressure test, if the gauges don’t read the same, it means one of two things: either you haven’t waited long enough for the pressures to equalize, or the orifice tube, expansion valve, compressor reed valves are stuck, or there is a severe restriction somewhere in the system that is preventing the pressure from equalizing.

In that situation, you must first address the issue at hand.

Troubleshooting incorrect static pressures

Listed below are the most likely reasons of static pressure readings that do not match the temperature/pressure chart and are excessively high (which is the most common).

  1. Leaks have introduced air into the system
  2. The system has been overcharged
  3. The refrigerant has been polluted

What 0 static pressure means

Because of a large leak, the entire air conditioning system is completely depleted. Find the source of the leak and rectify it before refilling.

What are normal AC gauge pressures when the system is running?

Generally speaking, you want a low pressure of roughly 27 psi and a high pressure of around 200 psi. What’s the deal with 27 psi? In an R-134a air conditioning system, 27-psi. on your gauge indicates that the refrigerant will create around 32°F at the evaporator (as long as the orifice tube/expansion valve is functioning correctly and there is no air in the system artificially inflating the pressure to 27-psi.). The temperature of water is barely below the freezing point at that position. R-134a pressures are typically 2.2 to 2.5 times higher than the ambient temperature entering the condenser, which is considered excessive.

At 200-psi, the refrigerant entering the condenser will have a temperature of around 130°F.

Normal high and low AC ambient temperature pressure listing

Temperature of the surrounding environment in degrees Fahrenheit The readings from the low side pressure gauge and the readings from the high side pressure gauge 65°F Low side pressure (25-35 psi) is present at the ambient temperature. High side pressure (between 135 and 155 psi) 70°F Low side pressure (35-40 psi) is present at the ambient temperature. Side pressures of 145-160 psi are common. 75°F Low side pressure (35-45 psi) is present at the ambient temperature. Side pressures of 150-170 psi are common.

  1. 85°F Low side pressure (45-55 psi) is present at the ambient temperature.
  2. 90°F Low side pressure (45-55 psi) is present at the ambient temperature.
  3. High side pressure of 275.300 pounds per square inch 100°F Low side pressures of 50-55 psi are typical.
  4. 110°F Pressure on the low side of the atmosphere is 50.55 psi.

How to test AC pressures with a manifold gauge

Set the air conditioning settings to MAX and RECIRCULATE. 2. Increase the speed of the blower. 3. Shut the doors behind you. It is possible to have windows open. 4. Once you have connected your gauges and started your engine, maintain a constant RPM range of 1,200 to 1,500 RPM.

Keep in mind that the pressure in the air conditioning system and the temperature in the central duct are directly proportional to the outside temperature and relative humidity. If your pressure and temperature measurements are outside of the normal range, please consult the section below.

What the AC gauge pressures mean

First and foremost, in order to effectively assess AC pressures while the air conditioner is operating, you must be aware of the sort of air conditioning system you are working on. Is it a cycling clutch orifice tube system or an expansion valves system that you’re talking about? It’s impossible to diagnose by pressures if you don’t understand the difference. See this page to find out what sort of air conditioning system is installed in your car.

Low and High AC pressures are nearly the same

If the compressor is functioning (the middle piece of the pulley is turning), the compressor is spinning but is not pushing any air into the system. Typically, this is an indicator of an issue with the compressor. Consult this thread for troubleshooting information if the center pulley is not turning properly.

Symptoms of a bad AC compressor

You notice that the low and high side pressures are nearly identical (for example, 80 psi low side and 80 psi high side) and that you must increase RPM significantly to bring pressures back into normal range; you also notice that the air only gets cold when you’re driving; and you’ve ruled out a low refrigerant charge and a bad orifice tube/expansion valve.

Low and High AC gauge pressures are high with no fluctuation

System overcharging, a lack of airflow over the condenser (clogged fins, radiator/condenser fans not working or not operating at the right speed), or the presence of air and moisture in the system are all possible causes. The following actions should be taken if the AC pressures are high: 1. Inspect the front of the air conditioning condenser (which is located in front of the radiator) to ensure that the fins are not blocked. 2. Inspect the radiator fans to ensure that they are operating at the right speeds.

Low and High AC pressures are lower than recommended on an orifice tube system

Low cooling efficiency is a symptom. Readings of pressure: The low side is really low. On the high side, it’s typical to somewhat low. Low refrigerant charge is one of the causes. It is in this situation that the evaporator is deprived of refrigerant. When using a fixed orifice tube system, you want the evaporator to be almost entirely filled with refrigerant before starting the compressor. The full evaporator will spill some boiling refrigerant into the accumulator, where it will continue to evaporate before entering the compressor if the system is adequately charged.

This frequently results in evaporator icing, which is the accumulation of ice on the evaporator.

Low refrigerant charge causes superheat

It’s important to remember that air conditioning works when the refrigerant removes just enough heat from the air to cause the refrigerant to shift from a liquid to a vapor. In an evaporator that is only half filled, on the other hand, the vapor absorbs heat. This is referred to as superheat, and in an orifice tube system, it is the superheated refrigerant that creates evaporator icing on the evaporator coil. In other words, because of the low refrigerant charge, the refrigerant in the system is allowed to sit in the evaporator for an excessive amount of time.

For starters, it absorbs enough heat to induce the refrigerant to transition from a liquid to a gaseous form.

THEN, as the gas absorbs even more heat from the evaporator airflow, the temperature of the evaporator falls below the freezing point of water, causing it to overheat. Any moisture in the air freezes on the evaporator fins very quickly.

Test for evaporator freeze-up

Test for evaporator freezing by turning off the engine and driving away from the car for a short period of time. When you return, take a look at the size of the puddle under the car. A huge puddle indicates that evaporator ice has melted and drained onto the ground, causing the water to pool. Alternatively, continue driving the car with the blower on HIGH while keeping an eye on the airflow coming from the vents. When the evaporator ices over, you should notice a significant drop in the amount of air that comes out of the vents.

The ice will be melted by the blower.

Then you’ll start getting chilly air again—at least until the evaporator re-freezes.

Please keep in mind that limited airflow through the evaporator, which can be caused by a clogged cabin air filter, might produce symptoms that are similar to those of a low refrigerant charge.

Restricted or plugged orifice tube can also cause low pressure on an orifice tube system

Restriction on the system’s low-end performance. When a limited orifice tube is present, the compressor will suction, but the restriction/clog in the orifice tube inhibits the full flow of refrigerant, resulting in starving of the evaporator (see illustration). When the low-side pressure falls below the low-pressure switch threshold, the compressor is turned off automatically.

What causes orifice tube restriction?

The orifice tube screen becomes clogged as a result of metallic wear particles from the compressor. During the course of time, rubber hoses degrade and rubber particles block the orifice tube screen. As a result of the reaction of moisture in the system with refrigerant and oil, acids and sludge are formed, which clog the orifice tube screen. A buildup of moisture in the system that freezes at the orifice tube, preventing refrigerant from flowing through the orifice. A leak in the air conditioning system permits moisture to enter the system.

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As a result, moisture condenses at the orifice tube, preventing refrigerant from entering the evaporator since the temperature is close to the freezing point of water.

If the gauge reading returns to a very low suction-side reading, it is probable that the orifice tube or expansion valve screen has been stuck in place.

Alternatively, if you have access to the orifice tube, you can heat the orifice tube while monitoring system pressures. If the system pressure returns to normal after you’ve applied heat to the orifice tube, it’s possible that moisture has entered the system and caused the problem.

The orifice tube is the wrong size

The orifice tube is significantly too big. Although the orifice tube has been changed, the O-ring has not been correctly seated. In other words, the mechanism is unable to generate pressure.

Low side AC pressure is VERY low and high side pressure is low: restriction

AC pressures at the low and high end are lower than required in an expansion valve system when the valve is situated on the evaporator outlet. The expansion valve is stuck open, preventing the system from building pressure. Alternatively, the thermal bulb that detects evaporator temperature is not functioning properly, resulting in the expansion valve remaining open.

Low and high side AC pressures are normal but the air isn’t cold

It is possible that the air conditioner is functioning properly but that the “hot” is turned on, reducing the effectiveness of the air conditioner. If you have a stuck air temperature door, a bad air temperature/blend door actuator, or an older system with a stuck open heater control valve, you may be experiencing hot engine coolant flowing into the heater core even when the heat is set to cold. What to look for:

Check heater control valve

The air conditioning may be functioning well, but the “heat” is turned on, which reduces the effectiveness of the air conditioning system. If you have a stuck air temperature door, a bad air temperature/blend door actuator, or an older system with a stuck open heater control valve, you may be experiencing high engine coolant flow into the heater core even when the heat is set to cold. Among the things to look out for are

Check air temperature or blend door and actuator

If the cabin air temperature is regulated by an air temperature/blend door, examine the operation of the actuator to verify if it moves when the temperature setting is changed. In some circumstances, changing one actuator is all that is required to make the problem go away. Try manually moving the air door if the actuator moves but the door doesn’t open or close. Many times, the door will become stuck or even come loose from its hinges.

Check the cabin air filter

Yes, it works in the same way as a furnace filter. If it becomes blocked, it might cause ventilation to be restricted. This, in turn, causes the evaporator to freeze, resulting in the AC being turned off. Don’t skip over this section. Many do-it-yourselfers update their air conditioning components only to realize that their cabin air filter is blocked after spending hundreds of dollars on replacement parts.

Check for a dirty evaporator coil

A build-up of leaves and dust on the fins of an evaporator coil might impair the coil’s capacity to effectively remove heat from your vehicle. Remove the blower motor resistor and have a look inside the evaporator coil to gain access to the coil. Cleaning the evaporator coil with a foaming chemical cleanser is recommended. More troubleshooting advice using gauges may be found in this thread. 2020 Rick Muscoplat is a professional musician. Rick Muscoplat posted a blog entry on

Gauge Readout Tool

When troubleshooting an air conditioner, the first tool to use is the gauge pressure.

The following table lists seven different gauge readouts that you may come across. When diagnosing an air conditioner, use the Gauge Readout Tool either alone or in conjunction with the table of Gauge Diagnostics.

Gauge Readout Tool

Conditions that are considered normal The presence of air in the cooling system (insufficient suction) The expansion valve is not working properly. Excess refrigerant is used. Intrusion of Moisture There is no circulation of refrigerant. Table of Gauge Data Summary Diagnostics

Normal Conditions

1 Environment Room Temperatures of 30-38 C (86-96 F) Engine Speed of around 5000 rpm Back to the top 1500 rpm, or around 75% of the rated engine speed

Air in cooling system (insufficient suction)

Pressure Variables Low-pressure range: 36 to 50 psi High pressure ranges from 284 to 356 psi. IndicationsBoth pressures are EXTREMELY ELEVATED The pipe on the low-side is not chilly. Causes Air in the system is the cause of the problem. Immediately shut off the system. Recharge the refrigerant system. Check the readings on the gauges. If the system is used for an extended period of time with air in it, the liquid tank must be changed. Return to the top of the page

Defective expansion valve

Pressure Variables Low-pressure range: 30 to 36 psi High pressure ranges from 313 to 327 psi. Indications Both pressures are EXTREMELY ELEVATED. Causes Charge of refrigerant that is not correct The expansion valve is not working properly. Installation of the temperature sensor was not done correctly. Remedy Check the amount of refrigerant in the system. Check the installation and insulation of the temperature sensor. Replacement of the expansion valve is recommended if the refrigerant charge is satisfactory and the temperature sensor installation and insulation are correct.

Excessive refrigerant

Maximum and Minimum Pressures On the low side, pressures range from 30 to 36 psi On the high side, the pressure ranges from 313 to 327 pounds per square inch. Indications Both pressures are EXTREMELY ELEVATED Causes Charge of refrigerant that is insufficient. Expansion valve that is not working correctly. An incorrect placement of the temperature sensor Remedy Check the charge of the refrigerant. Check the installation and insulation of the temperature sensor before using it. Replacement of the expansion valve is recommended if the refrigerant charge is satisfactory and the temperature sensor installation and insulation are both proper.

Moisture Intrusion

The Pressure Range is defined as follows: Low pressure ranges from 30 to 36 psi. On the high side, the pressure ranges from 313 to 327 psi. Indications Both pressures are EXTREMELY STRONG. Causes Inadequate refrigerant charge Expansion valve that is not working properly Installation of the temperature sensor was not done properly. Remedy Verify the amount of refrigerant in the system. Check the installation and insulation of the temperature sensors. If the refrigerant charge is satisfactory, and the temperature sensor installation and insulation are both satisfactory, then the expansion valve should be replaced.

Refrigerant does not circulate

Pressure Variables Low pressure range: 0 to -29.99 psi High pressure ranges from 71 to 85 psi. Indications The low pressure side transforms into a vacuum. As previously said, there is a lot of pressure. Frost or condensation on the front and rear pipe connections of the receiver dryer or expansion valve are signs of a faulty receiver dryer. Causes The air conditioning system gets clogged by pollution or ice. The AC system has been shut down due to a faulty expansion valve or temperature sensor.

Remedy IMMEDIATELY DISCONTINUE OPERATION Examine the area for pollution or ice.

If the expansion valve is not functioning properly, it should be replaced. Replace the receiver dryer with a new one. Refill the system with refrigerant to the right level. Hoses that are kinked should be repaired. Return to the top of the page

Summary Table of Gauge Diagnostics

The pressure on the low pressure side is TOO HIGH. When the high pressure side is excessively high, the low pressure side will often become excessively high.

Cause Inspection Remedy
Defective Thermoswitch The magnetic clutch switch turns off before the outlet air temperature is sufficiently low. Replace the thermoswitch
Poor Expansion Valvetemperature sensor contact The high and low pressure sides gauge pressures equalize when the magnetic clutch is turned off (within a short time duration) Replace Compressor
Expansion Valve opens too far Frost has adhered to the suction hose / pipe Install the temperature sensor against the low pressure pipe and cover with insulating tape.
Clogged compressor suction filter Compressor fitting is cool but the low pressure hose is not. Remove and clean the filter.

The pressure on the low pressure side is WAY too low.

Cause Inspection Remedy
Insufficient Refrigerant There is little temperature difference between the low and high pressure sides. Repair any leaks and recharge the refrigerant to the correct levels.
Clogged liquid tank(receiver dryer, accumulator) Considerable temperature difference between the inlet and outlet sides of the receiver dryer during operation. Also, tank may be frosted Replace liquid tank (receiver dryer)
Clogged expansion valve Expansion valve inlet side is frosted. Generally the low side pressure is near vacuum. Replace expansion valve.
Expansion valve temperaturesensor gas leak(damaged capillary tube, etc.) Expansion valve outlet side is chilled and low pressure side is LOW. Clean or replace expansion valve.
Clogged or blocked piping Low pressure readings decrease or a negative reading is shown. Indicates piping is clogged or blocked between the evaporator coil and the compressor. A frost spot may indicate the point of blockage. Clean or replace piping.
Defective thermoswitch(cold control) Evaporator is frozen showing ice along the face of the coil, not just frost on the manifolds of the coil. Adjust temperature sensing tube to a cooler part of the coil or replace the thermoswitch.

The pressure on the high pressure side is TOO HIGH.

Cause Inspection Remedy
Poor Condenser cooling Dirty or clogged condenser fins, Cooling fans do not operate correctly. Clean and / or repair the condenser core / fans.
Excessive refrigerant Verify by gauge reading Utilize your refrigerant recovery equipment to capture excess refrigerant. Charge to the correct refrigerant levels.
Air in the system Pressure is high on both high and low sides Evacuate, vacuum and recharge with refrigerant.

The pressure on the high pressure side is TOO LOW.

Cause Inspection Remedy
Insufficient refrigerant Little temperature difference between the low and high pressures. Repair any leaks and recharge the refrigerant to the correct levels

R134a Pressure Gauge Readings

HOW TO UNDERSTAND YOUR GAUGES If your employees are unable to read the gauges, they are unable to comprehend air conditioning. Despite the fact that this is a fundamental introduction to gauge reading, it is only applicable to the vast majority of cars; as such, it should only be used as a guide. Prior to testing, the vehicle should be recovered, cleaned, and charged to ensure that it is in good working order. If you are reading your gauges, there are a handful of fundamental factors that you should keep in mind — THE TEMPERATURE IN THE ROOM The system should be recovered, vacuumed (for a minimum of 20 minutes), and recharged after each use.

In summer, when the air conditioning is switched off, the pressure will be low, and on cold days, the pressure will be high.

TURN OFF THE AIR CONDITIONING

AMBIENT TEMPERATURE (CELCIUS) R134a PRESSURE (PSI)
0 30
10 45
15 55
20 70
25 80
30 100
35 115
40 130

Pressure and temperature will vary in tandem; as one rises, the other will rise, and as one falls, the other will fall, as one rises, the other will fall. It is expected that different refrigerants would have varying numbers. Understand what normal gauge readings are and how they differ from one another. TURNING ON THE AIR CONDITIONING

AIR TEMP (C) RED GAUGE (PSI) BLUE GAUGE (PSI)
0 40-50 20-30
10 50-100 20-30
20 100-150 20-30
30 150-200 25-35
40 180-225 25-35

As the ambient temperature rises, the red gauge increases in pressure (from 40psi to 225psi), but the blue gauge remains at a constant low pressure (40psi) (20psi to 35psi). When the fan is activated, the red gauge stops climbing, which is normally between 180psi and 225psi. TYPE OF COMPRESSOR It will be described only the two most prevalent systems – manual air conditioning and automatic climate control – in order to keep things simple. MANUAL A/C – The compressor is either fully operational or completely inactive (the familiar clicking sound as the compressor engages).

When the pump is turned on and off, the gauge readings will be as shown above.

When it achieves the desired temperature it reduces the amount of refrigerant being forced through the system (there is no clutch plate to click on or off, it is internally regulated).

As previously stated, the gauge readings will be as follows initially; however, once the vehicle has reached the proper temperature, the compressor will begin to pump less refrigerant through the system.

When less refrigerant is being pumped, the pressure displayed on the red gauge will be lower than when more is pumped.

AMBIENT TEMP RED GAUGE (PSI) BLUE GAUGE (PSI)
0 30-40 20-30
10 40-60 20-30
20 60-120 20-30
30 120-150 25-35
40 150-180 25-35

When the appropriate temperature is attained in chilly weather, the red gauge will only slightly raise, giving the appearance that the compressor is not working, which is not the case. Illustrations of flaws

  1. If neither of the gauges moves, this indicates that the compressor is not pumping. Fuse, pressure sensor, fan belt slippage, relay, wire break, lack of gas, compressor failure are all examples of possible defects to look for. A high reading on the red gauge indicates that the compressor is pushing against a stalemate. This happens when there is a blockage on the suction side of the compressor (blue gauge), which causes the pressure to drop. Filter blockage, crushed pipe, too much gas/oil, and a clogged thermal expansion valve are all examples of possible defects.
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As pressure increases, the temperature increases as well, which means that the pipes, filters, and other components will be HOT up to the point of the blockage and COLD (perhaps freezing) immediately following the obstruction.

  1. If the red gauge reads more than 225psi, check to see if the fan is operating properly. Possible fan switch failure
  2. This might be a single switch near the condenser or a combination of the fan switch and the pressure switch (assuming the pressure switch has four wires)
  3. The vehicle’s cooling system is inadequate. All of the foregoing are possible faults, as well as – condenser air flow restriction, vacuum duration that is too short, contaminated refrigerant (a/c unit that has not been serviced on a regular basis)
  4. If the red gauge is too low and the blue gauge is too high, the engine will overheat. Possibility of problem – the compressor has degraded to the point that it is unable to generate sufficient pressure on the discharge side (red gauge) or sufficient suction on the intake side (blue gauge)

Finally, if a system is turned off and has approximately 10% of its full charge remaining, as long as there is some liquid refrigerant in the system, the pressure gauges will continue to read the relevant pressure for the ambient temperature, i.e. 70psi at 20 C. However, when only vapour is present in the system, the pressure gauges will read a lower pressure. As a result, recover, vacuum, and charge at every opportunity.

What do ac manifold gauge readings mean?

Readings from a variety of gauges. A manifold gaugeset is used to measure the pressure of refrigerant within an air conditioning system. An car air conditioner is divided into two sections: the high side and the low side, which are separated by a metering mechanism and the A/C compressor. When the low side is high and the high side is low, the compressors are not performing as they are supposed to. The readings from the gauges will be affected by the temperature of the surrounding environment.

TYPE OF COMPRESSOR.

AMBIENT TEMP RED GAUGE (PSI) BLUE GAUGE (PSI)
10 40-60 20-30
20 60-120 20-30
30 120-150 25-35
40 150-180 25-35

In addition to the aforementioned, what are the usual pressures for r134a? In other words, the usual operating pressure of R134A in such a system ranges between 22 and 57psi under normal operating conditions. Similar to this, you can wonder what the high and low side pressures should be. At 90 degrees Fahrenheit or less, the low – side pressure should be about 30 PSI. When the pressure is much lower or greater than normal, there is a concern. The high-side pressure on a well functioning system will be approximately twice the ambient temperature + 50 PSI.

A value of 25 pounds per square inch (psi) to 40 pounds per square inch (psi) is ideal for a low pressure gauge.

Diagrams: System Pressure Chart

Find out what an average A/C system looks like, as well as the compressor manufacturer and what the R-134a requirements are for your particular automobile in this fast video.

R-134a TEMPERATURE PRESSURE CHART(Tabla de Temperaturas y Lecturas)
AmbientTemperature °F / °C(Temperatura Ambiental) Low-Pressure Gauge(Puerto de Servicio del Ladode Baja Presion) High-Pressure Gauge(Puerto de Servicio del Ladode Lado de Alta Presion)
65°F (18°C) 25-35 psi / 172-241 kPa 135-155 psi / 931-1069 kPa
70°F (21°C) 35-40 psi / 241-276 kPa 145-160 psi / 1000-1103 kPa
75°F (24°C) 35-40 psi / 241-310 kPa 150-170 psi / 1034-1172 kPa
80°F (27°C) 40-50 psi / 276-345 kPa 175-210 psi / 1207-1448 kPa
85°F (29°C) 45-55 psi / 310-379 kPa 225-250 psi / 1551-1724 kPa
90°F (32°C) 45-55 psi / 310-379 kPa 250-270 psi / 1724-1862 kPa
95°F (35°C) 50-55 psi / 345-379 kPa 275-300 psi / 1896-2068 kPa
100°F (38°C) 50-55 psi / 345-379 kPa 315-325 psi / 2172-2241 kPa
105°F (41°C) 50-55 psi / 345-379 kPa 330-335 psi / 2275-2310 kPa
110°F (43°C) 50-55 psi / 345-379 kPa 340-345 psi / 2344-2379 kPa
Ambient temp is the outside atmospheric temperature.
INTERPRETING PRESSURE READINGS
Low-PressureGauge High-PressureGauge ActionRequired
IN RANGE IN RANGE A/C is working properly.
LOW LOW Add Refrigerant.
LOW HIGH Need service, possible blockage of theexpansion valve or orifice tube.
HIGH LOW Needs service, possibly faulty compressor.
HIGH HIGH System is overcharged. Slowly removerefrigerant. Venting is illegal in USA.
It is illegal to vent 134a refrigerant into the atmoshpere.

AC Manifold Gauge Readings

A manifold gauge set is used to measure the pressures of refrigerant within an air conditioning system. The high and low sides of a car air conditioner are separated by a metering device and the air conditioning compressor. When the clutch is engaged, a compressor draws low-pressure vapor in from the suction side of the system through the intake. It compresses the gas and discharges it at a greater temperature and pressure via the discharge side of the compressor. These pressures and temperatures are extremely predictable, and they are influenced by the ambient or outside air temperature conditions.

It is possible that the compressor is not operating correctly when the low side is high and the high side is low.

Pressures are equalized and very near to each other when a system is static, meaning that it is not in action at the time.

Occasionally, a faint hissing sound can be heard while the pressures are equalizing and soon after the system has been shut down. As the compressor wears down and becomes weaker, the high and low side measurements of the system begin to approach static values more frequently.

How to Use A/C Manifold Gauges

The fact that your car’s air conditioning system is spewing hot air instead of cool air is a huge annoyance. The use of an A/C manifold gauge, as well as some interpretation of the gauge values, is required in order to determine the likely reason of the A/C issue. Some vehicle air conditioning repair procedures may be completed by the do-it-yourselfer, while others may necessitate the hiring of a professional auto air conditioning technician.

Step 1

Using the blue low-side hose, connect it to the low-side port on the air-conditioning unit.

Step 2

Connect the high-side hose (red) to the high-side port on the air-conditioning unit’s high-side port.

Step 3

Open both valves to allow the gauges to detect the pressure in the A/C system.

Step 4

Comparing the real PSI measurements to the regular PSI readings with the A/C system turned off will provide some interesting results (static pressure). The usual pressure measurement should be between 80 to 105 PSI on both the high and low sides of the gauge. Turn the A/C system’s output to the “max/high” setting. Check the low side PSI reading, which should be between 25 and 35 PSI when the engine is running at about 1,000 RPMs, and then check the high side PSI reading, which should be between 200 and 350 PSI when the engine is running at approximately 1,000 RPMs.

If the PSI readings remain below normal, replace the yellow hose.

  • The connections on the low and high hoses are of different sizes. The manufacturer’s owner’s handbook for your car’s make and model may specify precise PSI ranges. Depending on whether the PSI readings are normal and the system is still blowing hot air, you may need to check with an auto air conditioning specialist.
  • There are two distinct sizes of connections on the low and high hoses. If your automobile is of a certain make and model, the owner’s handbook may include precise PSI ranges. Depending on whether the PSI readings are normal and the system is still spewing hot air, you may need to visit an auto A/C specialist.

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They refer to the gas in an air conditioner as refrigerant. Over time, refrigerant may leak, and low refrigerant is one cause for an air conditioner to stop cooling.Many other thingsalso cause the system to not cool. Without diagnosing the real problem, adding more refrigerant may destroy the compressor and worse.

What to do when an air conditioner stops cooling

Biographical Information about the Author. A professional writer wrote this piece, which was then edited and fact verified using a multi-point auditing system to guarantee that our readers only received the most accurate information. Please visit our about us page by clicking on the link below to send your questions or thoughts, or to just learn more.

Basic automotive air conditioner pressure testing

R134A is the most commonly used automotive refrigerant today. R1234YF is a fuel that may be found in newer automobiles, and it is expected to become increasingly prevalent in the future. It is not addressed in this post how to diagnose R1234YF systems because they are different. Although the pressure in older systems differs somewhat from that of R134A, the basics remain the same. R12 is used in older systems. A refrigerant gauge set will consist of two gauges for measuring refrigerant. Indicators on the left are indicated in blue, and they are used to read the low-side of the system.

  1. Attachment to the system is accomplished by the use of a blue and a red hose.
  2. The majority of R134A gauges include quick-connect fittings on the hoses that allow them to be connected to the proper port.
  3. The gauges should only be fitted or removed while the engine is not running, regardless of the setup.
  4. By purging the lines, you will be able to eliminate this air and keep it from entering the system.
  5. Any air in the system will be forced out of the hose by the pressure in the system.

When using quick-connects, the hoses will seal when they are removed, and purging should not be necessary again in the future. If the system does not have an automated seal, it is possible that the lines may need to be cleansed after each usage.

What is static pressure in the system?

The static system pressure can be measured prior to the vehicle being started up. The pressure in both gauges should be very close to being the same. The actual pressure will vary depending on the kind of refrigerant used and the temperature of the surrounding environment, and it will not indicate whether or not the system has been adequately charged. R134A has a pressure of around 90 pounds per square inch when heated to 85 degrees Fahrenheit. Readings that are significantly lower than expected indicate that the system is low on charge or polluted with air.

Finding and fixing leaks will be explored in further detail in the following Detailed Topic.

What is normal automotive air conditioner pressure?

The engine should be started, and the air conditioner should be turned on. Actual measurements will vary depending on the temperature of the environment. When the temperature is 90 degrees Fahrenheit or less, the low-side pressure should be about 30 PSI. When the pressure is abnormally low or high, it indicates that there is a problem. Ideally, the high-side pressure will be approximately twice the ambient temperature + 50 PSI in a well functioning system. For example, on a 90-degree Fahrenheit day, twice 90 is 180, plus 50 equals 230 pounds per square inch of pressure.

Given that both pressures are within these limits, the system should generate a vent temperature in the mid-to-low forties while running the engine idling at a constant speed.

A chilly line indicates that the problem is most likely under the dash, with the actuators or with the doors.

This is called reheating.

What does higher than normal air conditioner pressures mean?

Low and high-side pressures that are significantly greater than normal are quite harmful. Compressors for air conditioners are designed to work within a specific temperature range. Higher than usual pressure will deform the aluminum casing, resulting in the compressor failing in a short period of time. The coils in the evaporator will also leak as a result of the high pressure. This may be highly expensive, as it is typically necessary to remove the dash in order to rectify the problem. The lack of air movement through the condenser and the overcharging of the system are the two most common causes of greater than normal air conditioner pressures, respectively.

It is also possible that a worn fan clutch or dirt obstructing air passage through the condenser is causing the problem.

A condenser fan turning does NOT mean it is moving sufficient air

Many electric fans and clutches are capable of operating at various speeds ranging from 15 percent to 100 percent of their maximum capacity. A faulty module or sensor may cause the fan to turn too slowly, resulting in insufficient cooling of the condenser.

The same is true for a fan clutch, which may function at a variety of speeds. It is advisable to leave the testing of air flow and fan speed to those who are well-versed in the procedure.

How does a system get overcharged?

It is possible to overcharge an air conditioner as a consequence of the addition of refrigerant, oil, or air that has remained in the system. Extracting the contents and measuring them is the only method to determine if there is an overcharge. Overcharging is frequently caused by adding extra refrigerant to a system without first determining why the system is not cooling properly. When a line on an air conditioner system is opened, air is allowed to enter the system and cool the room. The same thing might happen if the refrigerant seeps out and the system is completely depleted.

  1. Due to the fact that air takes up space, applying the appropriate charge results in an overcharge.
  2. Oil is used in a variety of components, including compressors, condensers, and accumulators.
  3. When there is insufficient oil in the system, the compressor will burn up.
  4. Oil takes up space, and adding it in a haphazard manner might result in an overcharged system after the right amount of refrigerant has been added.
  5. Replacement compressors must also be drained and measured before they can be used.
  6. This is a problem.

What does it mean when the low-side is high, and the high-side is low?

In order to remove heat from the car, the compressor reduces the low-side pressure and raises the high-side pressure. A broken compressor will not be able to make as big of a difference on both sides. While this occurs, cooling will be reduced, especially when the vehicle is at rest. It is possible that increasing the engine speed will bring the pressures closer to what is required. Compressors that operate in a clean and oiled atmosphere have a long life. If a compressor is malfunctioning, the fundamental cause must be identified, else the problem would return.

The low-side is way too low and the high-side too high

In most cases, insufficient low-side pressure on a fully charged system is the result of a restrictive component. A blocked orifice tube is a typical source of these types of issues. As the compressor tries to drive the refrigerant past the obstacle, the high-side pressure may become higher as a consequence. This will soon suffocate the compressor’s oil supply, resulting in a catastrophic breakdown of the machine. When imposing any limitation, it is necessary to take the source of the trash into consideration.

Why would both gauges read low?

Lower than normal pressure, on both gauges can show a system low on charge. Such conditions can also be caused by a malfunctioning variable displacement compressor. The contents of the system should be evacuated and measured to learn which condition exists. Adding additional charge may cause pressure to rise but may also create overcharge damage.Any of these conditions may also occur in unison. For instance, a restriction and a weak compressor could occur together. This condition could give varying readings. A good overall inspection, vent temperature measurement and gauge readings will isolate many air conditioner problems. After the problem is fully determined,quality repairof the system is possible.Please also see:Part one, electrical problems with air conditionersPart three, finding and repairing air conditioner leaksPart four, preventing and repairing compressor failure Post or Read Comments (2)

R134a High and Low Side A/C System Temperature Pressure Chart

This chart shows how the ambient temperature connects with the refrigerant charge pressure in the system, as well as how it impacts the high and low side psi readings on the system.

Recharging refrigerant or diagnosing an a/c system based on pressure readings from your gauges are also possible uses for this device.

Ambient Temperature (°F) Low Side High Side
110° 50-55 psi 335-345 psi
105° 50-55 psi 325-335 psi
100° 50-55 psi 300-325 psi
95° 50-55 psi 275-300 psi
90° 50-55 psi 250-275 psi
85° 50-55 psi 220-250 psi
80° 45-50 psi 175-220 psi
75° 40-45 psi 150-175 psi
70° 35-40 psi 140-165 psi
65° 25-35 psi 135-155 psi

A/C System Pressure Troubleshooting

This temperature and pressure relationship charge, when used in conjunction with a pair of high and low side gauges, may be utilized to diagnose an a/c compressor that is not functioning properly. There is insufficient refrigerant charge to meet manufacturer specifications on the low side and high side pressures. The air conditioning compressor is not engaged, and the variable displacement is not operational. Performance of the air conditioning compressor is degrading. Both the low-side and high-side pressures are elevated, and the refrigerant charge exceeds the manufacturer’s specifications.

Condenser is clogged and ventilation is obstructed.

Side Pressure is at a low level.

System constraint at a high level A/C compressor breaking internally due to pressures being equal or close to same The variable displacement feature of the A/C compressor is not operational.

What Should my AC Pressure Be?

Identifying the pressures present in your car’s air conditioning system may provide nearly all of the information you want about how well your system is performing at any one time. AC pressure used to be difficult to measure and necessitated the use of expensive gear, but thanks to technological advancements and the assistance of local auto parts stores, measuring one component of your air conditioning system has become much simpler. AC refill cans are widely accessible at your local car parts store, as well as at many bigger retail establishments.

  1. Using one of these gauges to detect the low side pressure in your system might be a pretty precise and economical method.
  2. If you look at your air conditioning system from the perspective of pressure, it is divided in two.
  3. This is due to the fact that the can of refrigerant you got from the auto parts store is pressurized, allowing it to force additional refrigerant through the system.
  4. It takes a more sophisticated piece of equipment to measure the pressure on the high-pressure side of your system.
  5. Get the right tools for your system from your local auto parts store if you want to measure the high-pressure side of it the most accurately.
  6. Now that you’ve discovered a safe and dependable method of measuring your air conditioning pressure, you’ll need to know what to look for.
  7. The greater the pressure will be outside, the warmer it will be outdoors.
  8. Because leaks are a prevalent problem in automotive air conditioning systems, if you notice that you have low pressure on the low side of your system, it is most probable that you have a leak.
  9. You may have an overfilled system if you have just added refrigerant, which might indicate a malfunctioning compressor.
  10. A low pressure on the high-pressure side of the system can also indicate that you have a low refrigerant level, or if the pressure on the high-pressure side is almost the same as the pressure on the low-pressure side, it can confirm that you are experiencing compressor problems.
  11. In order to fix the majority of air conditioning system issues, a vacuum, repair, and refill of the system are required.

For additional information about Red Angel A/C Stop LeakConditioner, including how it works and how to use it, please see the banner to the right! You may also get Red Angel A/C Stop LeakConditioner from any of our partnered auto parts retailers, such as the ones listed below:

  • Identifying the pressures present in your vehicle’s air conditioning system may provide nearly all of the information you want about how well your system is performing at any one time. Although measuring the pressure of your air conditioning system used to be difficult and expensive, thanks to technological advancements and the assistance of local auto parts stores, measuring one component of your air conditioning system is becoming more simple. AC refill cans are widely accessible at your local auto parts store, as well as at a number of bigger retailers. Many of these refill cans are equipped with a pressure gauge, which allows you to learn a little bit more about what’s going on in your system and to make educated guesses about how much refrigerant to dispense while you’re filling them. When it comes to measuring the low side pressure in your system, these gauges are quite precise and cost next to nothing to buy. The low side pressure is only one component of the picture, which is unfortunate. When it comes to pressure, your air conditioning system is divided in two. Your air conditioning system maintains a very high pressure between the compressor and condenser and up to the expansion valve, and a comparatively low pressure after the expansion valve and into the evaporator and back to the compressor’s input valve. This means that the fresh refrigerant will be pushed into the system by the pressurized container of refrigerant you got from the auto parts store. In order to ensure that you receive the maximum amount of refrigerant out of the can and into your system, you should connect it to the lower pressure side of the system, such that the low side pressure displayed on the gauge on the refill can is the pressure you want to see measured. It takes a more sophisticated piece of equipment to measure the pressure in the high-pressure side of your system. In your high-pressure system, the pressures are so high that you need specific hose and connection materials as well as a particular gauge in order to keep the pressure under control and prevent any refrigerant from escaping into the atmosphere. Get the necessary instruments for your system from your local auto parts store if you want to measure the high-pressure side of it the most effectively. I think this set of A/C Manifold Gauges would be fantastic. Having a safe and dependable method of measuring your AC pressure is now all that remains. You just have to know what to look for. Based on the system, pressures can differ from one automobile to another, and the pressure in your system will fluctuate with changes in the surrounding environment. In addition, the higher the temperature outdoors, the greater the pressure. You can use this chart of R-134a system pressures as a general reference for now. Because leaks are a prevalent problem in automotive air conditioning systems, if you notice that you have low pressure on the low side of your system, it’s most probable that you have a leak. Another possibility is that you have a blockage somewhere in your system, which would explain the low pressure. You may have an overfilled system if you have recently added refrigerant, which might indicate a failing compressor. However, if you have recently added refrigerant, you may have an overfilled system as well. If you have a low pressure on the high-pressure side of the system, it may also indicate that you have a low refrigerant level, or if the pressure on the high-pressure side is close to the same as the pressure on the low-pressure side, it may indicate that you are experiencing compressor problems, as well. If you’ve just serviced your system, a greater pressure here might suggest that it’s overfilled, but more often than not, it’s an indicator of a clog in the system’s drainage system. In order to fix the majority of air conditioning system issues, a vacuum, repair, and refill of the system are necessary. Leaks, on the other hand, are problems that may be resolved by simply addingRed Angel A/C Stop leak Conditioner via the low-pressure port in your system! If you want to learn more about Red Angel A/C Stop Leak Conditioner, including how it works and how to use it, click on the banner below! Red Angel A/C Stop LeakConditioner is also available at any of our associated auto parts retailers, including:

Knowing what the pressures are in your car’s air conditioning system may tell you practically everything you need to know about how well your system is working. AC pressure used to be difficult to measure and necessitated the use of expensive gear, but thanks to technological advancements and the assistance of local auto parts stores, measuring one component of your air conditioning system has become much easier. Auto parts stores, as well as many bigger retailers, carry air conditioning refill cans.

Using one of these gauges to detect the low side pressure in your system might be a pretty precise and economical option.

When it comes to pressure, your air conditioning system is divided in two.

As a result of the pressurized can of refrigerant you got from the auto parts store, the fresh refrigerant may be forced into the system.

It need a more sophisticated piece of equipment to measure the pressure on your system’s high-pressure side.

Get the necessary tools for your system from your local auto parts store if you want to measure the high-pressure side of your system the most accurately.

Now that you’ve discovered a safe and dependable technique to test your air conditioning pressure, you’ll need to know what to look for.

The greater the pressure is outside, the warmer it is outdoors.

Because leaks are a prevalent problem in automotive air conditioning systems, if you discover that you have low pressure on the low side of your system, it is most probable that you have a leak.

You may have an overfilled system if you have recently added refrigerant, which might indicate a malfunctioning compressor.

A low pressure on the high-pressure side of the system can also indicate that you have a low refrigerant level, or if the pressure on the high-pressure side is almost the same as the pressure on the low-pressure side, it can confirm that you have compressor problems.

The majority of air conditioning system faults will necessitate a vacuum, repair, and refill of the system.

Click on the banner below for more information about Red Angel A/C Stop LeakConditioner, including how it works and how to use it. You may also find Red Angel A/C Stop LeakConditioner at any of our partnered auto parts retailers, such as:

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