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Why is A/C Pressure Too High? Find Causes and Solutions

Why is A/C Pressure Too High? Find Causes and Solutions

Why is A/C Pressure Too High? Find Causes and Solutions

Even with the introduction and use of modern technology, your car’s air conditioning (A/C) system sometimes falters. The common problem that we always encounter is why the A/C pressure too high. When this happens, do you know the causes? And how do you find soluti​ons  to these problems?

If these problems persisted and not properly address on time, the damage may cost you a fortune. A total overhaul is too costly, as well as the replacement of parts. Here are some possible causes of why is your car’s air conditioning pressure is sometimes too high and know the roots of this and the best possible fixes.

Know the pressures on an A/C system

Pressures on an A/C system

Pressures on an A/C system - Via: yourmechanic.com

Before we discuss the various causes of this problem, it is necessary that you know the type of pressures involved in an A/C system. There are 2 pressure types that you must consider: the high-pressure side and the low-pressure side. Normally, it is the former (high-pressure side) that is always the issue.

The low-pressure side pertains to the vacuum pressure (lower than atmospheric pressure) of the refrigerant (or coolant) before it enters the compressor. On the other hand, the high-pressure side is the pressure of the refrigerant as it exits the compressor.

Condenser fan not working

Why is A/C Pressure Too High Car AC Condenser Fan

Car AC Condenser Fan (Via: Amazon)

This is the common cause of abnormally high pressure on your A/C system. As the refrigerant enters the condenser (from the compressor) to liquefy the coolant, it must be cooled by the fan. If the fan is not properly working, the condenser will have the difficulty of condensing the coolant. Have your fan replace or check up by a knowledgeable mechanic/ technician.

Modern cars are sometimes controlled by a computer, including the A/C system. If the fan is working (meaning it is revolving), check its speed, it might be with an abnormal speed not enough to cool the condenser.

If you find that the fan is working well, you might search for other causes.

The system might be overcharged

Why is AC Pressure Too High add refrigerant

Add refrigerant

It is advisable that you do not add refrigerant during this time to avoid damage to the evaporator core. Too high a pressure may result in a leak on the evaporator’s thin aluminum and its folded seams, the condenser piping, and other thin parts of the piping system.

Additionally, once you experienced high pressure, it is an indication that the system has enough refrigerant. Adding more coolant could possibly knock down the compressor over time or the evaporator’s copper tubes. The common refrigerant used in a vehicle’s A/C system is the R134A. For this refrigerant, the standard pressure setting is as follows:

  • For 18 C temperature (minimum)
  • Low-pressure side : 25-45 psi
  • High-pressure side: 135-155 psi

This standard pressure is on the lowest setting of 18C, which is the common comfortable temperature inside your car. However, the pressures will vary in increments once you opt for an increase or decrease of the temperature inside your car.

Contaminated A/C coils or piping

Why is AC Pressure Too High car evacuating the coolant out of the system

Evacuating the coolant out of the system

Another possible cause of too much high-pressure might be the piping system has leaked or has the incorrect use of refrigerant oil. Leaks may cause air or water to contaminate the system. Either of these 3 causes will require you to evacuate (or vacuum-pump) the coolant in the system.

Furthermore, if ever both the low-pressure and high-pressure sides have high readings, check out the sight glass. If you notice bubbles inside the glass, you are more convinced of evacuating the coolant out of the system.

Vacuuming the whole system is required to avoid further contamination of the pipeline. Expert technicians use the Robinair Vacu Master to evacuate coolant from an A/C system of cars. Consult your expert mechanic/technician about this. And let him do the necessary fixes as this undertaking needs special skills, like flare-welding of leaking copper pipeline, etc.


Now you know what are some of the causes of why A/C pressure is too high in your car. You now also knew the best solution to your dilemma. Better still, just remember that there is nothing impossible when you know the ways. And it could save you precious dollars.

Evacuating the coolant from your A/C system is the best way possible when there is no problem with the fan or if circumstances told you to do so. The do the necessary steps to fix the problem. Anyway, there are expert people who could do this for you.

We will be happier if you share your comment with us and we promise to give you more information about the best car care in town.

Just remember these things when you are in doubt of the performance of your car’s air conditioning system.

  • Check high-pressure and low-pressure sides.
  • Check condenser fan.
  • Check refrigerant.
  • Do not overcharge refrigerant.
  • Check for contamination of the system, and finally,
  • Always ask your mechanic/technician for advice. And let him do the necessary repairs.

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