What Can Cause AC Low Side Pressure To Be Too High?

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AC low side pressure too high

Air conditioning is a wonderful invention. We are certainly used to living with it and having it keep us cool and comfortable. Having air conditioning in our cars is also a wonderful automotive feature! You can’t imagine summer driving without it.

We are so accustomed to being able to regulate the temperature for our personal preference, but what happens when we can’t do that? When this happens, we need to take a look and try and figure the cause and then how to fix it.

AC low side pressure too high
AC low side pressure too high

What can cause my AC’s low side pressure to be too high?

If you notice that the AC in your car is not working right, there can be several reasons why. You need to figure out the reasons so you will know what steps to take when fixing it. You can start by looking under the hood yourself. Try and see if any obvious reasons jump out at you. You can see debris, ice, blockages and broken parts. If not, you may need to take your car in for servicing.

Some common problems are:

  1. High pressure inside the condenser pan can cause the evaporator coils to leak
  2. Your car might be experiencing low air flow or no air flow through the condenser. This usually happens when there is a bad motor in the fan. Or you may have some debris around the motor or fan that is restricting the air flow.
  3. Your car’s AC system may be overcharged. This means there is too much coolant in the AC system. And sometimes it can be caused by too much oil in the system.
AC’s low side pressure to be too high
AC’s low side pressure to be too high

Let’s look at the condenser first.

Checking the condenser for blockages or debris is a good start to figuring out why the pressure is too high. In this case, the high pressure side would continue to have a high reading, and the low side pressure will continue to drop.

So, open the hood of your car and check the condenser and the surrounding area for any debris or blockages. You should remove and clean out any that you see. Then, check your pressure again. If the readings are still off, then you need to check for deeper problems.

If you have a normal high side reading and a high low side reading, then you might have a thermostat switch malfunctioning. This thermostat switch will need to be replaced by a mechanic.

What about if your AC system is overcharged?

An overcharged AC system in your car can also cause your pressure readings to be off on the low side. This is a situation that will also need to be corrected. To do this, you will need to remove refrigerant from the AC system. Ideally the reading should be at 30 psi for the low side pressure. You can purchase pressure gauges online or in stores in order to check the pressure yourself at home.

If you have to, discharge some of the refrigerant following these steps.

  1. Switch the thermostat to off
  2. Connect the low pressure side to the suction side of the compressor
  3. Use a wrench or hex key to close the service valve
  4. Close the high pressure side’s valve, but leave it slightly open
  5. Use a low voltage jumper to engage the compressor
  6. The low side pressure should start to empty
  7. When it reaches the vacuum level, close the valve completely
  8. Now disengage the compressor

Is it my evaporator coils?

It is possible that your car’s evaporator coils are cracked and leaking and this is why your pressure readings are off. In this case, you will need to take your car to a mechanic for repairs. If you have a problem with the coils in your car’s AC system, that could also cause icing. The icing can then cause a problem with the pressure by blocking the flow of air.

Could it be a problem with the condenser fan or fan motor?

The condenser fan in your car’s AC system does operate at different capacities and different speeds. It is very possible that any kind of malfunction with the condenser fan would reduce its speed and also its efficiency. This in turn, will result in the inability of the fan to cool the system properly and allow proper airflow. When find your error in your car, you also should use the obd2 scanners to find the code.

Final Thoughts

We are accustomed to being able to turn on the AC in our cars and adjust it to our comfort levels. When there is a problem, we need to figure out the cause right away and take steps to correct it.

Since the AC system in cars can be an expensive repair, it is important that you find out the issue sooner, rather than later. If you notice that your car’s AC low side pressure is too high, there can be a few reasons why this is happening.

First, check the thermostat switch. Make sure this switch is not cracked or broken. Then make sure it is not being obstructed in any way. Many times, you will need to bring your car to a mechanic to have this switch checked and replaced. If the switch is working fine, you need to look further.

It is also possible that your pressure readings are off because there is too much coolant in the AC system. You will need to remove some coolant from the AC system to get your pressure readings back to normal ranges. This can be done by yourself with a few tools, or you can bring your car to the auto shop.

Some other issues that can cause your pressure readings to off include frozen lines, icing, oil in the compressor, compressor fans not working properly or cracked and leaking coils. All of these scenarios do require a certified mechanic to fix them.

Anytime you notice that your car’s AC system is not working properly, you should get it checked immediately. Blowing warm air or not working at all are not just an inconvenience, but could be a sign of a bigger problem.

Mike Cross

Mike Cross

You have to look for teachers. If you want to be a mechanic, go hang out with mechanics.

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