Understanding AC pressure switch

The AC pressure switch keeps track of the high pressure level in the A/C loop and turns on or off the compressor based on two pressure thresholds. The cooling fan is controlled by a separate circuit that secures the condensation process by forcing air through the condenser.

AC pressure switch

On the high-pressure side of the loop is where the pressure switch is situated. Your entire AC system may stop working properly if the AC pressure switch is broken. Well, in this article, you’ll get to know the definition, function, symptoms, location, testing, and cost to replace the AC pressure switch.

Read more: Understanding Pressure Gauge

Let’s get to it.


What is the AC pressure switch?

The AC pressure switch serves as a safety switch that is mounted both on the high and low sides of the ac system. Both the high-side and low-side pressure switches are used to monitor the system for pressure defects that could harm the compressor.

The compressor runs the risk of being damaged when the pressure is too low since it uses less oil. When it is too high, there is a chance that the compressor will overheat and suffer damage. The switch will shut off the compressor to prevent harm if the pressure goes too high or too low, depending on which side of the system the sensor is mounted on.

The proper operation and lifespan of an AC system depend on the pressure switches; therefore, if they are causing issues, they should be replaced since they safeguard the compressor and the rest of the system from harm.

AC pressure switch function

The AC pressure switch’s function is to provide safety monitoring to the AC system. It is in charge of keeping track of the refrigerant pressure on the AC compressor’s low and high pressure sides. The high-pressure side is monitored by one, while the low-pressure side is monitored by the other.

Function of AC pressure switch

The low-pressure switch makes sure the pressure never drops too low. When a leak develops, this issue arises. When refrigerant is pumped out of the AC compressor at an improper pressure, the compressor may suffer serious damage, which will increase the cost of repair.

The high-pressure switch keeps track of any systemic obstructions that could increase pressure on the high-pressure side. It is possible for the system to explode if the pressure becomes too high. In order to prevent further pressure buildup, the switch instructs the system to turn off power to the air conditioner.

Location of the AC pressure switch

The pressure switches are found on the air conditioning pipes, on both sides of the air conditioning compressor. On the low-pressure side (smaller pipe), you can find the low-pressure AC switch, and on the high-pressure side, the opposite switch (large pipe).

Location of the AC pressure switch

Additionally, the high-pressure switch is placed after the AC compressor, whereas the low-pressure switch is placed before it. While some manufacturers place their AC pressure switches somewhere else, the majority are located in the engine compartment. You may find the right spot for your model by checking the service manual for your vehicle.

How to test the AC pressure switch

Below are well-detailed steps on how to test the AC pressure switch:

Turn on the air conditioning and scan for any error codes.

Turn on the air conditioning to its maximum setting while the engine is running. Make sure the windows are open to prevent the air from cycling. When the air conditioner intermittently cuts off, that is the first sign that the pressure switch is faulty. The windows should not be left open while this is occurring.

Using an onboard diagnosis system (OBD) is one of the best ways to check a broken A/C pressure switch. Your A/C system’s error code(s) might reveal a lot about its condition. You can use a code scanner to look for DTCs using your car’s OBDII port.

Once the issue has been fixed, you may also utilize the code scanner to clear codes. If you don’t have an engine code reader, you could swing by your neighborhood auto parts shop, where they might provide the service without charge.

In the case that an AC pressure switch circuit error code is discovered, the AC pressure switch must be replaced even if the wires to the switch appear to be in good condition. A low refrigerant level may also be to blame if the error code indicates that the pressure is too low.

Examine the electrical connections

You can perform the AC system check manually if your car lacks a scanner that can do it for you. Checking a wiring diagram and repair instructions for your specific car model should be your initial step. A pressure switch for your AC should have two or three wires.

Normally, there are only a signal wire and a ground wire if there are two wires. A 5 volt wire, a signal wire, and ground are most likely present if there are three wires. However, a wiring diagram is required to verify this.

Use a multimeter to check the Ohms between the signal and ground pins. When the switch is open, you should see an open circuit and 0 ohms, respectively. The AC pressure switch typically closes when the pressure is accurate and functioning properly.

Additionally, you can check the AC pressure switch connector to see if it has 5 volts, ground, and a signal coming from the engine control module. You must inspect the wiring if there is a problem with the values. But to do this, you need a wiring diagram.

Inspect the AC pressure

Use your air conditioning gauge set to check for adequate levels on both sides if your AC pressure switch looks to be working properly. The low-pressure gauge and low-pressure fitting will be connected one to the other.

When the outside temperature is 90 degrees or less, you should get readings on the low-pressure side that are close to 30 PSI. With 50 PSI applied, the high-pressure side should be about twice as warm as the surrounding air. You could need to refill the refrigerant if the low or high pressures are incorrect, or there could be a more serious issue with the system.

The cost of replacing the AC pressure switch

Since there is a check valve inside the AC pipe that prevents the refrigerant from pouring out even if the AC pressure switch is removed, you often do not need to empty and refill the coolant system when replacing the AC pressure switch. To make sure that this is the case with your particular car model, carefully remove the AC pressure switch.

However, the cost to replace an AC pressure switch ranges from $50 to $300 on average. The cost of the AC pressure switch will probably be between $20 and $100, and the labor cost will depend on how difficult it is to get to the sensors.


What does an AC high-pressure switch do?

Your AC unit is protected from high pressure by high-pressure switches. If the pressure becomes too high, these switches will turn the AC system off. On the other hand, low-pressure switches are made to safeguard your AC unit from low pressure. If the pressure falls too low, the switch will turn the AC system off.

How do you know if your AC pressure switch is bad?

Your AC pressure switch has to be replaced if the AC is intermittently switching on and off, failing to cool the cabin, or not starting the compressor.

Where is the AC pressure switch?

You can find your AC pressure switches on the unit’s high and low sides. These switches, which have separate switches for the high side and the low side of the system, continuously check and monitor the refrigerant pressure on both sides of the system in an effort to keep the compressor from being harmed by pressure problems.

Does a car’s AC have a low-pressure switch?

Two switches in the air conditioning system of your car guard the refrigeration circuit and the compressor. In order to protect the compressor from harm, the low-pressure switch disables the system when the pressure drops too low. It has a limited lifespan, just like every other component of your car.

How do I reset my AC pressure switch?

Find the high-pressure switch close to the compressor (a cylindrical device piped into the refrigeration system with two wires and a red button on the top). In order to reset, push the button. Restart the device by pushing the rocker switch.

How do I fix my AC pressure switch?

  • Find the A/C pressure switch.
  • The negative battery cable should be disconnected.
  • Take out the switch’s electrical connector.
  • Remove the switch.
  • Replace the switch.
  • Put the electrical connector back in place.
  • Reinstall the negative battery cable.
  • Test the A/C.

What causes furnace pressure switch failure?

The following are some of the more frequent reasons I’ve observed furnace pressure switches failing or not closing sufficiently to allow the rest of the system to fire up: a blocked port on the pressure switch’s collection chamber. a blockage in the flue. a trapped or ruptured diaphragm.

What does a car AC pressure switch do?

The pressure switch keeps track of the high pressure level in the A/C loop and turns on or off the compressor based on two pressure thresholds. The cooling fan is controlled by a separate circuit that secures the condensation process by forcing air through the condenser.

How do I know if my car’s AC sensor is bad?

Common symptoms include warm air blowing from the vents, the AC working intermittently or not at all, and noise coming from the system.

Do I need an AC pressure switch?

To protect the compressor in this situation, the low AC pressure switch typically disables the entire air conditioning system. If the low-pressure switch is malfunctioning, the compressor may overheat and stop working. Therefore, it’s crucial to examine this switch and determine whether it has to be replaced if your AC isn’t blowing cold air.

What happens when your AC sensor goes out?

The air conditioner will just keep blowing cool air into the room if the temperature sensor stops measuring the temperature in the evaporator unit. This will cause the cabin to get excessively cold, which could result in higher energy costs and an uncomfortable interior temperature.

That is all for this article, where we discussed definition, function, symptoms, location, testing, and the cost to replace the AC pressure switch.

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