AC Pressure Switch

The AC is a system that allows you to get cool air on a hot summers day – all it takes is a flick of a switch and you’ll be rewarded with a cool breeze. It feels like heaven to be driving on the freeway while the AC is on but if you push the button to turn it on and it won’t turn on, this can be worrying. If you’re prone to sweating a lot, it’s important that you get the AC running again so your body heat can regulate better.

The AC system in your vehicle is a complex system and it operates with a dual system. On one side of the system, there’s refrigerant which is the fluid at low pressure and the other side has fluid at high pressure. The low-pressure fluid is a gas – it’s then passed through the compressor which liquifies it so it can go through the AC system and into a component called a receiver. The air is then cooled down and blown through the system leaving the compartment as cool air – this is what you feel. The refrigerant that’s at high pressure then leaves the system so it can come through the low-pressure side where it’ll become a gas again. From here, the cycle will start again.

What is the AC Pressure Switch?

The AC pressure switch is a switch that’s placed on the high and low sides of the air conditioning system. This switch measures the pressure on the high and low sides of the AC. There are two switches mounted on the AC, a high and low on and they both monitor for any pressure faults that would break the compressor. If the pressure monitored is too low, then the compressor can be damaged. If it’s too high, then the compressor can overheat and damage. The compressor can burst which will cause the refrigerant to leak.

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The pressure needs to be in the middle so that the compressor doesn’t risk getting damaged. If any of the high and low switches measure a pressure that’s too high or too low, then the compressor is turned off, so it won’t be damaged. Since the pressure switches protect the compressor which is the part that allows the AC to function, they’re an important part to the ACs system and since they protect it from getting damaged. If the pressure switches are bad, then the compressor can end up breaking meaning you won’t have a cool AC system.

AC Pressure Switch Symptoms

There are a few symptoms that you’ll experience if the AC pressure switch becomes faulty or is no longer working. Some signs are more common than others and they’ll signify that there’s a problem with the AC. If you want to know for definite that the AC pressure switch is faulty, then you check it using an OBD2 scanner. This is a diagnosis tool that reads the error code that has been returned to the control unit. A professional OBD2 scanner (View on Amazon) will tell you what the error code means on the display screen. If you buy a standard one, you’ll have to write down the error code and look up the meaning in the specification manual.

AC Not Turning On – If the pressure switch detects that the pressure is incorrect, the AC system could be overridden and stop the compressor from activating. Its job is to protect the compressor from damage when the pressure is noticed to be too low or high. In this case, when you try and turn on the ac, you’ll notice that no cool air comes out of the cabin. This is a major indicator that there’s a problem with the AC pressure switch.

AC Comes on But Nothing Happens – sometimes the pressure switch can be activated but nothing will come out of the AC system. The pressure switch needs to be able to manage the refrigerant’s pressure as it goes through the system. If one or both of the switches aren’t working correctly, then the AC system won’t be receiving the correct pressure readings from either side of the system. This means that AC won’t be working at the rate it should. You’ll notice that the car might take longer to get cool or anything coming out of the AC is really weak.

AC Cutting On and Off – If the AC cuts on and off rapidly, then this could be a sign that the switch isn’t working properly. A normally functioning AC should be switching on and off periodically – this happens when the proper temperature for the ac has been reached and the pressure is enough. If you notice that the AC constantly turns on and off rapidly, then there might be something wrong with the AC. You’ll be able to notice this symptom if you’re used to the way the AC operators because you’ll notice that it just cuts off periodically when the temperature has been reached.

When the pressure switch is damaged, then you’ll notice that it cuts off a lot quicker and more frequently than normal – you’ll notice that the AC doesn’t have to reach the right temperature for this to happen, it just happens. This is because it’s not cutting out because it’s actually doing its job, it’s cutting out because the AC pressure switch is giving incorrect readings to the AC control.

Car Not Getting Cool – if the AC pressure switch fails, then the compressor will be disengaged, and the car won’t be able to cool down properly. If you notice that you’re getting air, but the air isn’t cool enough, this can be a sign that the pressure switch is failing. If the pressure isn’t good, then cold air won’t be able to leave the cabin.

Air not at Correct Temperature – if the air leaving the cabin isn’t at the correct temperature, then this can be a sign that the pressure switch isn’t working at all. When you set a specific temperature for the AC, the air leaving the AC should be the same as this temperature. If the air coming out isn’t at this temperature, or it’s taking a long time to reach the desired temperature, this is and indication that the pressure switch is faulty or not working correctly.

Compressor not Coming On – if the compressor isn’t coming on, this is a sign that the AC switch isn’t working properly. The pressor switch Is meant to control the function of the compressor and a failing pressure switch can stop the AC compressor from working at all. The compressor pumps the refrigerant through the entire system and if it doesn’t work, the refrigerant can be evaporated with cool air meaning that the cabin won’t get change temperature.

Preventing the Failure of the AC Pressure Switch

If you’ve noticed any of the symptoms above, chances are the AC pressure switch is failing or it’s bad. In this case, you’re going to have to replace it or get it repaired. The key to making sure this part doesn’t go bad is to service and maintain your vehicle often – this means that you’re checking and maintaining key components in the vehicle so that you avoid having to visit the mechanic. If you know what you know now, then you’ll probably still have a functioning AC system.

If you want to avoid AC problems and save $100s of dollars that you’ll spend at the auto repair shop, you’ll need to service your vehicle often – you can use our mechanic-rated Auto Maintenance and Repair Manual to do this. It’s basically what mechanics use to go through your vehicle to check if there are any problems that need fixing. As soon as they notice the most minor problem, they’ll ask you to fork out some money even though it’s a problem you can fix yourself in minutes – the manual will teach you how to maintain your vehicle every few thousand miles and it’ll teach you how to fix minor problems that mechanics will ask you to pay for; saving you money in the long run.

A lot of our readers have the Auto Maintenance and Repair Manual printed on their garage wall and 92% of them haven’t visited the auto repair shop in the last year because they know what to do to avoid problems. All it takes is giving your vehicle a little attention every few thousand miles and you’ll never spend money at the workshop again.

Replacing the AC Pressure Switch

The best part about a failing or bad AC pressure switch is that you can repair it yourself. The AC compressor switch (View on Amazon) can be purchased at a moderate price and it can be easy to replace. Before you replace any switch, you’ll need to know the located and disconnect the battery.

AC Pressure Switch Location

If pressure switch location different in a lot of vehicle and this also depends on if you want to replace the high- or low-pressure switch. Most pressure switches can be found in the engine bay or on the front of the AC condenser. If you want to replace the high-pressure sensor, then check the small pipes under the hood to locate it. If you want to find the low-pressure sensor, check the larger pipes so you find the sensor. If the pressure sensors are obstructed, then you’ll need to remove some parts in order to reach it. If you’re unable to find any of the sensors, then you can check the specification manual and you should be able to find a wiring diagram that’ll let you find the pressure sensors.

Disconnect Negative Terminal

To replace any switches or sensors, the battery needs to be disconnected. Before you do this, you need to be aware that disconnecting the battery might reset the radio and the computers in the vehicle. To disconnect the battery, you need a wrench and you’ll need to unscrew the negative nut.

To help you with this, you can leave the headlines on to make sure they’re fully drained. When the battery is completely drained, you need to wait for 15 minutes so the sensor can deploy – you won’t be able to work on the sensor while it still has power. Once the sensors have lost power, you can finally disconnect them and install a new one.

Remove the Electrical Connector

You need to use a wrench to loosen the sensor and unscrew it. Overtime, the sensor can get stuck, so you’ll need to apply extra pressure when you’re trying to unscrew it. If it does get stuck and you try to remove it, it can break the condenser or the pipe. Make sure to use some WD-40 (View on Amazon) to lubricate the sensor so it’s easier to remove. Once it’s been sitting for a while, you can try and remove it using the wrench.

If you see a check valve built into the sensor mount, this means that the AC system doesn’t need to be removed before you remove the sensor. Make sure to check the service manual for your vehicle before replacing the switch to check if there’s a check valve built it. If there is, removing it can result in the refrigerant pouring out. Once you’ve removed the old switch, you can fit the new switch using a to wrench. To avoid the sensor getting stuck again, you can apply some WD-40 before installing the new sensor. Once installed, make sure to reconnect all the connectors.

If this sounds like a big job to you, then you can just get a professional to do it. You can either contact your locate repair shop and they’ll be able to do it for you. You should know that this compressor at a price. The switch itself can cost anywhere from $20-$100. The labor can cost between $30-$100. You could end up spending $50-$100 depending on the problem you have.