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AC Pressure Switch: Everything You Need To Know

AC Pressure Switch: Everything You Need To Know

The AC pressure switch is responsible for controlling the activation of the compressor to avoid its damage due to very high or very low pressure.


 

The compressor receives a signal from the switch to stop running when the system has very low or very high pressure. When the pressure is very high, the compressor can be damaged due to overheating. When the pressure is very low, the compressor can be damaged due to low oil.

 

If you noticed that the AC system is not running, not blowing cold air, compressor not running, or the AC system is turning on and off very frequently, then this is a sign that you need to replace the AC pressure switch.

 

If you replaced the pressure switch on your own, you could save a lot on labor costs since the part itself is very cheap. However, you need to have a good understanding of the relationship between pressure, temperature, and refrigerant volume.

 

In this article, we will give you a detailed explanation of the AC pressure switch role, the symptoms of a bad AC pressure switch, the expected cost to replace the pressure switch, and how to replace it on your own.

 

What is the AC pressure switch?

 

The AC pressure switch is the part responsible for monitoring the pressure. When there is enough pressure for the compressor to run safely, if the AC pressure switch fails, the compressor will not receive a signal to start, and therefore, you will not have a running air conditioning in your vehicle. 

 

In every vehicle, there are two pressure switches, one on the high-pressure side, and one on the low-pressure side. 

 

Both switches are important in protecting the compressor from being damaged. If the compressor is running on low pressure, the compressor will get damaged because it is running on low oil. On the other hand, if the compressor is running on high pressure, it will get damaged due to overheating.

 

Usually, the AC switches will turn off the compressor if the pressure gets too high or too low to prevent it from getting damaged. 

 

What are the symptoms of a bad AC pressure switch?

 

There are several symptoms associated with a faulty AC pressure switch. Some of the symptoms are very commons, while others are rarer. While you can confirm the AC issue by reading trouble codes, these are some of the common symptoms of a faulty AC pressure switch:

 

  1. The AC system does not turn on:

 

As we mentioned before, the AC pressure switch is to protect the compressor from getting damaged by very high or very low pressures. 

 

In situations when the pressures switch is damaged, the switch might force the compressor from activating. Therefore, no cool air will be pushed out of the air conditioning system. 

 

Once the compressor does not receive a pressure reading from the AC pressure switch, every time you try to turn on the AC system, the AC system will not work.

 

  1. The AC system is not running continuously

 

In normal conditions, the AC system will cycle on and off to keep the desired temperature. For instance, the AC will keep going until the desired temperature is reached and will stop right after. It will then start again when the temperature gets higher than what the AC is set for.

 

However, if you notice that the AC system is switching on and off more often, this is a sign of a faulty AC pressure switch.

 

  1. The AC system can not cool down the car:

 

If the pressure switch has a problem, the AC system will not be able to cool the vehicle until the desired temperature. The compressor will not understand the pressure level, and it will take the cabin a longer time to reach the desired temperature than usual. 

In many cases of the faulty pressure switch, the AC system will not even reach the desired temperature at all.

 

  1. The compressor is not running:

 

The AC pressure switches are responsible for turning on and off the compressor. If the switches have a problem or are not working properly, the compressor will not run at all. 

 

The compressor is responsible for making the entire AC system do its job by pumping the refrigerant through the system. 

 

If the compressor is not working, there will be no refrigerant running through the AC system, and therefore, the AC system will stop functioning.

 

Common OBD codes for a faulty AC pressure switch.

 

Before you decide to replace your vehicle’s AC pressure switch, you need to confirm that the AC problem is coming from the AC pressure switch, not from any other wiring issues. 

 

One of the best approaches is to use an Onboard Diagnosis System (OBD) and read the error code. Some of the common OBD error codes that are associated with a faulty AC pressure switch are:

 

  1. P0745

 

This error says, “Pressure control solenoid malfunction,” which is a clear indication that you need to replace the control switch.

 

 

  • P0746:

 

This error says, “Pressure control solenoid performance or stuck off,” which means that you also need to replace the switch.

 

 

  • P0747:

 

 

This error says, “pressure control solenoid stuck on,” in this case, you also need to change the switch.

 

 

  • P0748

 

 

This error says, “pressure control solenoid electrical,” while this error might indicate a problem in the pressure switch, you need to check the electrical wiring before replacing the switch.

 

 

  • P0749

 

 

This error says, “Pressure control solenoid intermittent,” for this error, and you also have to check the electrical wiring before replacing the pressure switch.

 

Other error codes might be related to a faulty AC pressure switch. However, you need to check the wiring connection, the refrigerant pressures charges, before deciding to replace the pressure switch. Example of such errors are:

 

  1. P0530: A/C refrigerant pressure sensor circuit malfunction
  2. P0531: A/C refrigerant pressure sensor circuit range/performance
  3. P0532: A/C refrigerant pressure sensor circuit low input
  4. P0533: A/C refrigerant pressure sensor circuit high input

 

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

 

Replacing the vehicle’s pressure switch differs significantly by car’s make, model, and year. 

 

In the automobile world, the repair cost is divided into parts costs and labor costs. The AC pressure switch is one of the relatively cheap parts. On average, expect to pay between $20 to $100 on parts only. 

 

However, the cost gets much higher if you included the labor cost, especially if you are repairing it at a dealership, not at a local auto repair shop. The labor cost to replace an AC pressure switch can range from $30 up to $200 at some dealerships.

 

That is why it is recommended that you replace the AC pressure switch on your own if you have some sort of mechanical skills. Watching some of the YouTube videos on the same topic can fill the knowledge gap and help you replace it on your own.

 

While the mentioned above are the estimated costs for repairing the pressure switch, this type of repair is usually done within other more complicated repairs. 

 

For examples, here are some of the common repairs that are related to AC pressure switch replacement:

 

  • Replacing a cylinder head
  • Replacing a distributor cap
  • Replacing the suspension shock or struck
  • Replacing the timing belt
  • Replacing the yaw sensor
  • Replacing the parking brake activation switch
  • Replacing the steering center link
  • Replacing the blower motor switch

 

How to replace the AC pressure switch?

 

Replacing an AC pressure switch is one of the very straightforward vehicle repairs. It is recommended that if you have some mechanical understanding that you do it on your own. Replacing the AC pressure switch can save you a lot of money on labor costs, especially if you decided to repair it at a dealership.

 

While it is simple to replace the AC pressure switch yourself, you must have a good understanding of the relationship between pressure, temperature, refrigerant amount. This is because you need to avoid over-charging or under-charging the AC system, which is a common problem with many DIYs. 

 

While the replacement process might differ by vehicle’s make, model, and year, there are some simple steps that you can follow to replace the AC pressure switch:

 

  1. Find the location of the pressure sensor: Locating the pressure sensor differs by car make, model, and year. Besides, it differs if you are looking to replace the high- or low-pressure switches. 

 

In general, you could find the pressure sensors either in front of the AC condenser or in the engine bay.

 

Locating the high- versus low-pressure switches can be known by the pressure lines. Usually, high-pressure lines are larger than small pressure lines. Therefore, if you are looking to replace the high-pressure switch, look for large pipes under the hood and follow these lines to locate the pressure sensor. 

 

On the other hand, the low-pressure AC pressure switch can be located by following the small pipes under the hood. 

 

If you are looking to replace the high-pressure sensor, it is usually located under the condenser and be prepared to remove some parts before reaching the switch.

 

  1. Disconnect the battery negative cable

 

In many of the vehicle repairs, you must disconnect the negative battery cable. This way, you will prevent a short to the ground and, therefore, preventing yourself from injuries and preventing major damages to the electrical system.

 

Keep in mind that when you disconnect the negative cable from the battery, you might lose your radio and instrument cluster data. 

 

 

  • Remove the electrical connector:

 

 

Using a wrench, try to loosen the switch and unscrew it gently. 

 

Some switches might get stuck in place as they have been sitting there for a very long time. In this case, you might need to add WD-40 or 5-56 and leave the part in place for a couple of hours. Adding the WD-40 or the 5-56 can help loosen the switch and make it come off easier.

 

If you decided to push hard and try to force the switch to come off, you might result in breaking the pipes and cause major damages to the system. These damages might require much higher repair costs than replacing the faulty AC pressure switch.

 

Another important note is that some vehicles might have a check value connected to the AC pressure switch. If you tried to remove this type of switches, you might start seeing refrigerant pouring out of it.

 

Therefore, you need to consult the vehicle’s owner’s manual or the factory repair to confirm that your vehicle has a check valve connected to the pressure switch or not.

 

  1. Install the new AC pressure switch

 

now install the new pressure switch in the correct place. Make sure to tighten it appropriately using a torque wrench and lubricating the seals right before you install them.

 

 

  • Reinstall the removed parts: 

 

 

If you had to remove some other parts to install the AC pressure switch, it is the time now to reinstall these parts. 

 

How often should I replace my AC pressure switch?

 

In general, the AC pressure switch will not need to be replaced during the entire lifetime of your vehicle. 

 

However, more AC system usage can shorten the lifespan of the AC pressure switch. 

 

Therefore, there is no recommendation on how often you need to replace the pressure switch, and it simply replaces it when needed. 

 

Conclusion

 

The AC pressure switch(s) are very important for the AC system functioning. If you noticed any issue with the AC pressure switches, you need to get it fixed immediately to avoid high repair costs for the entire AC system.

 

Once you noticed any of the bad AC pressure switch symptoms, you need to get the vehicle diagnosed by a professional mechanic. The mechanic can confirm the symptoms and replace the switches if needed. This way, you can have a very good functioning AC system.