Symptoms Of A Bad AC Pressure Switch : Location & Replacement Cost

ac pressure switch

AC systems are a very useful part of cars and other vehicles. Some components in a vehicle’s air conditioning system are small, and some are large. Such as an AC high-pressure switch and a low-pressure switch.

AC pressure switches play a vital role in running the system as a whole. But sometimes, due to some reason, a pressure switch gets damaged, due to which many problems related to the air conditioning system are faced in vehicles.

Through this article, we will learn about AC pressure switches (high and low) in detail. Bad AC pressure switch symptoms, location, how to test, and how much it might cost to replace

What Is The AC Pressure Switch? (High & Low)


There are two types of AC pressure switches in an AC system. one high-pressure switch and one low-pressure switch. Both the pressure switches are connected to the AC system of each vehicle. They act in a way to protect the AC compressor. A high-pressure switch is installed in the refrigerant high-pressure line.

AC pressure switches can be 2, 3 and 4-pin, depending on the vehicle model. And a low pressure switch is installed in the refrigerant low-pressure line. Both of these pressure switches monitor the pressure of the refrigerant. so that the compressor of the AC can be saved from getting damaged in any situation.

How Does Car AC Pressure Switch Work?

AC Low Pressure Switch – When the refrigerant pressure is below normal, the oil in the AC compressor is not moving, which causes the compressor to be damaged due to friction, and the entire AC system of your vehicle may completely shut down.

The low-pressure switch sends a signal to the ECM when there is low refrigerant pressure. This causes the ECM to shut off the power supply to the AC compressor. Due to this, the AC compressor is saved.

AC High-Pressure Switch – Similarly, the high-pressure switch monitors the high pressure of the refrigerant. When there is high pressure in the refrigerant line, the AC compressor is prone to overheating, due to which the piston and rubber seal of the AC compressor can be badly damaged.

This high-pressure switch turns off the power supply to the AC compressor by sending a signal to the ECM when the pressure is high.

Symptoms of A Bad AC Pressure Switch (High & Low)

Symptoms of a faulty AC pressure switch (high and low) include irregular cooling, strange noise, frequent stalling of the compressor, inadequate cooling performance, the AC system not turning on, and possible damage to the compressor. These problems can arise due to improper operation of the AC due to an incorrect pressure reading from a bad pressure switch.

1. Sudden Start or Stop AC Compressor

ac clutch not engaging

A bad AC pressure switch can cause the AC compressor to shut off suddenly and walk on its own. And this happens even when the temperature of the evaporator is not even cold.

A bad AC pressure switch signals the wrong refrigerant pressure to the ECM, due to which the ECM suddenly stops or suddenly starts the power supply to the AC compressor.

2. AC System Strange Noise

Whenever you start the AC system of your vehicle with a bad pressure switch, you may then hear a strange noise around the evaporator under the dashboard of your vehicle. This strange noise may be different from engine noise.

Also, there will normally be a clicking sound of the AC compressor turning on, but the refrigerant flow may be obstructed, because a bad pressure sensor stops the AC compressor before the refrigerant pressure builds up.

3. Insufficient Cooling In The Cabin

If you keep your car’s air conditioning system on for a long time. But even with the cooling coming on, the temperature inside the vehicle is not cool enough.

This could also be a symptom of a bad AC pressure switch. Because a bad pressure switch does not allow the AC compressor to run continuously,

That means the AC compressor starts tripping fast, due to which the AC compressor starts shutting down even before cooling takes place inside the cabin.

4. Hot Air Flow From Vents


A bad AC pressure switch causes hot air to blow through the vents even when the AC system is on.

However, this symptom can also occur due to damage to other parts of the air conditioner system or low refrigerant. But if the pressure switch of your vehicle’s AC system is damaged,

You can still feel hot air blowing through the vents. because the bad pressure switch does not allow the AC compressor to turn on. Due to this, the pressure of the refrigerant drops and the air conditioning system stops working.

Where is The AC Pressure Switch Located (High & Low)

ac pressure switch

There are generally two types of AC pressure switches in vehicles. AC high-pressure switch and low-pressure switch

  • High Pressure Switch Location: The high pressure switch is located on the high pressure pipeline of the refrigerant.
  • Low Pressure Switch Location: The low pressure switch is located on the low pressure pipeline of the air conditioning.

How To Test AC Pressure Switch

If your vehicle’s AC system is not working properly and you suspect the pressure switch of the AC system to be faulty, then you can repeat the following process.

1. Scanning From OBD-II Scanner


First of all, you have to turn on the AC and use the OBD-II digital scanner. You need to scan your vehicle’s system through a digital scanner.

In this, you will find the trouble code related to the AC pressure switch. You will need to check the wiring, depending on the code that pertains to the AC pressure switch.

2. Check Wiring Connection


If the AC pressure switch trouble code is detected, check the wiring related to the AC pressure switch and see if its wiring is not cut or damaged anywhere.

If the AC pressure switch wiring is correct, then you will need to manually check the AC pressure switch for its readings with a multimeter.

If you find AC pressure switch correct by multimeter. Then you need to check the AC refrigerant pressure.

3. Check AC Refrigerant Pressure

ac pressure gauge

You have to use a pressure gauge to check the AC pressure. The connector of this gauge has to be connected to the low pressure point.

After this, you have to see the pressure of the refrigerant. If this pressure is lower than normal, you have to add refrigerant.

AC Pressure Switch Replacement Cost

On average, changing the AC pressure in vehicles can cost between $90 and $220. You may have to pay between $60 and $100 for a new AC pressure switch, and the labor cost for replacement by a mechanic can range from $30 to $120.

The replacement cost of a pressure switch in any vehicle’s air conditioning system depends on the make and model of the vehicle and the pressure switch, as AC pressure switches come with 2, 3, and 4 pins in different vehicles. Therefore, their prices may vary.

However, replacing the AC pressure switch can save you the cost of refilling the refrigerant. Because of this process, you will not need to remove the refrigerant again.

You can close the stop valve in the refrigerant pipeline while replacing the AC pressure switch. So that the refrigerant does not come out while changing the AC pressure switch.

How Do I Know If My AC Pressure Switch is Bad?

If your AC pressure switch is bad, you may experience irregular cooling, frequent cycling of the compressor, inadequate cooling, or the AC system not working at all.

For precise information, you can use the diagnostic tool to measure the pressure reading in the AC system to see if the switch is bad. If you suspect a faulty pressure switch, consider having it inspected by a professional mechanic for an accurate diagnosis and replacement.


Q. What does the AC pressure switch do?

The pressure switch in the AC system monitors the pressure of the refrigerant. The high pressure switch is mounted on the high pressure pipe, and the low pressure switch is mounted on the low pressure pipeline.

Q. What can a bad AC pressure switch cause?

A bad pressure switch can cause your vehicle’s AC compressor to overheat, due to which the rubber seals and pistons of the compressor may be damaged and your entire AC system fail. Then the compressor needs to be replaced.

Q. How much does it cost to replace an AC pressure switch?

Typically replacement AC pressure in vehicles can cost an average of $90 to $220.

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