Reasons for High Pressure in a Car A/C System

by Jennifer SimonUpdated August 08, 2023

Mechanics often misdiagnose high-pressure gauge readings in a car's air-conditioning system. Although mechanics tell owners that the high pressure is due to a problem with the accumulator or the evaporator coils, that is not likely the case. Most high-pressure readings are a result of the refrigerant or coolant not cooling adequately. Insufficiently cooled Freon automatically causes the pressure to increase. However, it’s important to know that your pressure readings will vary based on your high side pressure and low side pressure as well as the car's ambient temperature. To DIY a diagnosis for troubleshooting purposes, here’s a few reasons why you have high pressure in your car’s AC system.

Issues with the AC Condenser Fan

A common problem with HVAC systems in cars is issues with the condenser. The air-conditioner's condenser is responsible for receiving high-pressure and temperature refrigerant from the compressor clutch. The AC compressor is designed to dispel the hot air and cool any amount of Freon refrigerant in your car. The condenser should also be thoroughly cleaned and no debris should be present. Also, it should be checked to ensure that there is no blockage to the air flow.

Loose Fan Shrouds and Warm Air

An AC pressure switch up can be the result of loose fan shrouds or air dams. The fans and shrouds should be mounted securely to correctly circulate cool air. Tighten any of the appliances that are not positioned correctly or tightened adequately. Fans and shrouds are designed to run at specific speeds, so determine if any of the fans are running at a reduced speed. Replace any of the fans that are malfunctioning in order to restore the air-conditioning system's cooling abilities. The shrouds and fans are directly related to the cooling process, which will affect the amount of refrigerant in your car. Once the cooling issue is resolved the high-pressure gauge should return to normal.

Engine Cooling Problems

A common cause for irregular car AC pressure is an overheated engine. An overheated engine can be the result of many different issues, but an overcharged system is one of the most common. An overheating engine radiator can cause the air-conditioning system's pressure to increase significantly. Heat from the radiator transfers to the condenser and causes the pressure to rise due to the warmer and potentially low refrigerant level. It is possible the space between the radiator and the condenser has become clogged with build up or leakage from other parts of the system. The entire cooling system should be checked and cleaned thoroughly in order to solve the issue and to prevent further damage to the whole AC system.

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