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AC compressor valve blew the refrigerant out.

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17K views 48 replies 8 participants last post by wjfawb0 Jul 15, 2025

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If your AC compressor's pressure relief valve is blowing refrigerant, it indicates an overpressure issue. Here's a breakdown of potential causes and troubleshooting steps: * **High-Pressure Causes:** Overpressure can stem from poor airflow through the cooling system (blocked radiator/condenser), radiator/condenser air seal leaks, cooling fan issues, or internal compressor degradation blocking the metering system (TXV or orifice tube). * **Gauges are Essential:** Use a proper A/C gauge set to monitor both low and high side pressures. The high side pressure is likely the culprit. * **Normal Pressure Readings:** The fan should activate around 240 psi on the high side. The computer should disengage the compressor clutch at 431 psi. The pressure relief valve should activate between 497-570 psi. * **Expansion Valve:** A clogged or faulty expansion valve can cause high pressure. Replacing it, along with the receiver/drier, is a common step. * **Condenser:** If debris is found in the system, consider replacing the condenser, as it's difficult to flush effectively. * **Cooling Fan:** A malfunctioning or delayed cooling fan can cause pressure to spike, especially after the car has been sitting. Check the fan's wiring and connections, particularly the positive cable connected to the battery. * **A/C Pressure Sensor:** A faulty A/C pressure sensor can cause the fan to not engage at the correct pressure. * **TIPM:** A failing TIPM (Totally Integrated Power Module/fusebox) can cause overpressure issues. This may require professional diagnosis and repair.

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demarpaint

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Joined May 14, 2011

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#6 · Jun 22, 2022

If you plan on servicing AC systems you really need a good set of gauges, and learn how to use them. The simple store bought top off gauges can cause problems with either overfilling [more common] or under filling an AC system. Mechanics love those gauges.

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