AC High-Pressure Switch Symptoms

Air conditioning in a car gives a soothing feeling, especially when you are in traffic in hot weather conditions. Without a working air conditioning system, cars suffer from the heat no matter how much they wind down their car windows.

This is why the cooling system in the car is very important. If the AC high-pressure switch fails, there are certain symptoms you will notice. How do you solve the problem of a faulty AC high-pressure switch? This is what this post is all about.

When you have a High-Pressure Switch within your AC you will experience a variety of symptoms such as Repeated On/Off of The Car AC, No Cooling Effect in the Car & Compressor Not Activated. These are all the top three signs that your AC High-Pressure Switch is going bad. You will learn more about how the system works and other related difficulties.

How AC System Works?

Before you can understand the symptoms of a malfunctioning AC high-pressure switch, you have to learn the mechanisms of the AC system as a whole. The auto AC system works on two principles.

The first principle comes from the compressor, a part of the AC system that takes in the gas substance (refrigerant) and is connected to the bay engine area through the small high-pressure lines.

The temperature level of the refrigerant increases when it is compressed so that the gas flows toward the AC condenser. This principle makes the refrigerant turn to liquid from its gaseous state before pushing to the expansion valve.

Once the refrigerant reaches the expansion valve, the pressure suddenly comes down before it turns to vapor and then evaporates through the system’s evaporator. The refrigerant gains a lot of heat from the atmosphere, resulting in a temperature drop. In the process, the blower supplies cold air to the surroundings to produce cool air for the people.

A car’s air conditioning system consists of different components, from the compressor to the condenser, the expansion valve, the evaporator, the blower, and the air conditioning pressure switches. The air conditioning pressure switches are in two halves; the AC high-pressure switch and the AC low-pressure switch.

The AC high and low-pressure switch is placed in strategic places in the car’s air conditioning system to perform the important task of switching off the compressor when the pressure becomes too low or too high.

So what is the function of the AC high-pressure switch, and what happens when they go bad in the car? What are the symptoms of the AC pressure switch? These and others will be answered in this article. But first, let’s create a simple picture of the air conditioning system to better understand where the AC pressure switch comes in.

Air Conditioning Pressure Switch: How it Works

As mentioned in the introductory part, a car’s air conditioning system is made up of different components. The compressor, condenser, expansion valves, evaporator, and AC pressure switch. The compressor compresses the refrigerant gas that comes from the engine at high pressure. The temperature of the gas rises and moves to the condenser, which is located near the radiator.

In the condenser, the gas becomes liquid and is transferred to the expansion valve. As soon as the liquid gets to the expansion valve, the pressure suddenly lowers and becomes vapor before moving to the evaporator. The absorption of heat is done by the evaporator. This leads to the cooling of the gas. The cooled gas is now released by the blower into the car.

If you are reading closely, you will understand that the pressure of the gas is high when it moves from the compressor to the condenser and then to the expansion valve. Here there is a high-pressure switch, which turns off the compressor when the pressure is too high.

Likewise, a low-pressure switch is found between the expansion valve, where the pressure suddenly drops, and the evaporator, which releases cool air through the blower to the car. The low-pressure switch also turns off the compressor when the pressure is too low.

If the pressure is too high or too low, it could be detrimental to the entire air conditioning system. When the pressure is too high, the compressor will burst, which will lead to leakage in the compressor and the inability of the compressor to release the refrigerant to the condenser, which will end up leading to the failure of the entire air conditioning system.

Also, when the pressure is too low, there is an implication on the compressor. The compressor will suffer exhaustion, making it unable to compress the refrigerated gas. This will also impede the performance of the entire air conditioning system.

Without the AC pressure switch, the compressor will be vulnerable to damage. For cool air to get blown into the car, the compressor has to be in good shape all the time; that’s why AC pressure switches are important. A malfunctioning AC pressure switch is also bad for the entire air conditioning system.

Signs of a Bad AC Pressure Switch

There are different symptoms of a failing AC high-pressure switch that shows off. It takes a curious and careful AC user to note these symptoms before the issue deteriorates. If you notice any of the following signs, quickly swing into action to fix the AC high-pressure switch.

Repeated On/Off of The Car AC

This is one of the clear-cut indications that the car AC pressure switch is bad. Normally, the car air conditioning goes off when there is a balance in the amount of cool air and pressure and then comes back on when there is a slight imbalance. This is done by the AC pressure switch. When the AC high or the low or both pressure switch is bad or malfunctioning, the air conditioner comes on and off repeatedly and more rapidly.

No Cooling Effect in the Car

Yes, the air conditioner is activated and .working, but the car isn’t cool enough. If either of the switches is bad, there will be a problem maintaining the pressure of the air conditioner, thereby leading to no or low cooling effect in the car.

Compressor Not Activated

The AC pressure switch’s function is to turn on and off the compressor when pressure is too high or too low to avoid any form of damage. A malfunctioning AC pressure switch may not activate the compressor when needed. As we have established, the car’s air conditioner will not work if the compressor is not activated.

Replacing the Bad AC Pressure Switch

If you’re experiencing serious issues with your AC pressure switch, the first thing is to look for the symptoms in your car and then find a way to fix them. Once these signs are not giving way to repair, the easiest and the best solution is to do AC high- or low-pressure switch replacement. What can you do in the event a professional technician is not available to fix the issue?

Let’s take a look at these simple Do-It-Yourself steps for AC pressure replacement:

Locate the AC high-pressure switch
Disconnect the negative battery cable
Unscrew the faulty switch
Install and replace it with a new one

Step 1: Locate the AC pressure sensor

The first stage is to find the AC pressure sensor, whether low or high pressure. The sensor is often located in the engine bay section of your car. In some other cars, you’ll find your AC sensor beneath or on the front side of your car’s AC condenser. Sometimes, you may have to remove some or whole parts of the condenser before you can remove or replace the pressure sensor.

The low-pressure AC sensors are bigger than their high-pressure counterparts. Trace the small pipes you find right under the hood, and there you’ll locate your high-pressure sensor. To find a low-pressure sensor, follow the larger pipes under the hood.

Step 2: Take the sensor off the battery ends

After locating the pressure sensor, disconnect it from the negative battery terminals. Taking off the cables will keep the entire process safe for you. Also, this will prevent damage to your car’s entire electrical and wiring system. The cables, if not disconnected, could also result in a circuit shortage to the ground. Don’t forget there is a chance you will lose your instrument cluster while trying to disconnect the sensor from the battery. Your data may also be lost to the radio.

Step 3: Unscrew the sensor from the electrical connections

With the help of a wrench, you’ll have to carefully remove the sensor and loosen it from the electrical connector. The danger of not doing this is the possibility of damage to your condenser or pipe. Don’t forget the sensor has been there for a while and may have been stuck to the floor it’s sitting on. Check if there is an in-built check valve.

Step 4: Screw and install the new sensor

Having unscrewed and removed the old sensor, it is time to set up the one. Do not carry this process out until you have read the manual with your car. This will enable you to follow all specifications regardless of whether or not there are symptoms of AC high or low-pressure switch. Make sure you tighten all parts of the system back in place.

Frequently Asked Questions

Q: How do I check a faulty AC pressure switch?

To diagnose a bad AC pressure switch yourself, watch out for the intermittent on/off of your car AC. Also, you can check the evaporator, which has tubes that are cold to the touch. If those tubes are not cold, you have a faulty AC pressure switch. Another method is to use a pressure gauge.

Bear in mind that it is better and safer to let a certified technician diagnose your AC to get an accurate outcome. The result of the diagnosis will inform whether or not you have to take the Do-It-Yourself or go through a professional repairman.

Q: How does the AC pressure switch work?

The AC pressure switch comes in two forms, the high-pressure switch, and the low-pressure switch, and is placed in different positions in the air-conditioning system. When the pressure is too high or too low, the switch puts off the compressor to prevent damage to the compressor.

Q: How much does it cost to replace the AC Pressure Switch?

The cost of replacing the old AC pressure switch and installing a new one differs from one car model to another. Meanwhile, you may find the cost of purchasing the sensor cheap and reasonably affordable from your seller, maybe between $20-100.

However, your AC pressure switch’s replacement cost is much higher than that. Labor costs could rise to as high as $30-150. If the process requires removing and replacing certain important parts, you may pay up to $200.

Final Thoughts

I think we already have a proper understanding of how vital the AC high-pressure switch is. They ensure that the car’s air conditioning system works perfectly and also play an essential role in the durability of the entire air conditioning system. So any impediment of these components should be addressed to ensure the system’s reliability.

If you encounter any symptoms similar to those stated above, you should contact an expert technician to diagnose the problem and recommend the proper solution. The proper functioning of your car AC shouldn’t be a whether-or-not matter. Instead, it would help if you took it seriously, especially when summer approaches when the heat is at its peak.

AC High-Pressure Switch Symptoms

How AC System Works?

Air Conditioning Pressure Switch: How it Works