Does a car AC compressor have a pressure relief valve?
Yes, automotive ac compressors have a pressure relief valve installed on their body.
What does an ac compressor relief valve in a car do?
The AC pressure relief valve is a safety device that protects the compressor from operating above its designed Maximum operating/working pressure.
The high -pressure relief valve is used to keep the system pressures from reaching a point that may cause compressor lock-up or other component damage because of excessive high pressures. When ac system pressures in a vehicle exceed a predetermined point, the pressure relief valve opens, venting refrigerant and reducing the ac system pressure .
The ac pressure relief valve in a car can fail in 3 different positions.
- Pressure relief valve stuck fully open.
- Pressure relief valve partially open.
- Pressure relief valve stuck closed.
What happens if the pressure relief valve fails ?
Signs of the ac compressor pressure relief valve failure
- Pressure relief valve stuck fully open.
In this condition, the ac compressor will not be able to pressurize the ac system. The ac system will not hold the refrigerant charge for a long enough period to allow the ac compressor to raise the refrigerant pressure to normal ac operating pressures.
- Pressure relief valve partially open.
In this situation ,the ac compressor relief valve remains partially seated. This condition is the most difficult to diagnose. The a/c compressor will operate and pressurize the system up to normal operating pressures and the overall performance of the car a/c system will be excellent but will slowly decrease over time ,because of the refrigerant leaking out from the not fully closed relief valve.
- Pressure relief valve stuck closed.
This could result in a dangerous condition. The ac compressor pressure relief valve is a safety device intended to keep the refrigerant pressure circulating inside the ac system by the compressor below a dangerous point. The relief valve is the last safety resource used by the car manufacturer to vent the refrigerant out into the atmosphere before an ac component exceeds its safe working pressure and explodes. The ac compressor pressure relief valve is usually activated after all the other safety devices in the car were unable to stop the ac compressor operation.
Why is my air compressor pressure relief valve leaking ?
The air compressor pressure relief valve is a spring self-resetting device. The intended operation of the valve is to open when the refrigerant pressure inside the ac system exceeds a maximum pressure point ,usually between 350 PSI to 600 PSI. The normal operation of the relief valve is to open and vent refrigerant out into the atmosphere when the pressure exceeds the maximum level. The relief valve should reset automatically to the fully closed position when the refrigerant pressure is less than the internally calibrated spring force. In many cases once the valve opens it will not return perfectly to the fully closed position creating a refrigerant leaking point in the virtually sealed ac system.
What does the ac compressor pressure relief valve tell me about the overall condition of the ac system ?
- Engine cooling system affecting a/c performance
- Inoperative radiator fans
- Underperforming fan clutches
- Freon overcharge
- A/C system contamination
- A/C system contaminated with non-condensable gases
An ac compressor pressure relief valve fault should be the beginning of a deeper vehicle ac system diagnostic. A leaking pressure relief valve is a warning about an excessive high pressure in the ac system. Overlooking the warning sign of the valve could lead to expensive repairs in the automotive a/c system.
What happens when the ac compressor pressure relief valve in a vehicle is venting freon ?
- A/C internal compressor failure
- High side components leaking
- A/C poor performance
- A/C system contaminated with debris from internal compressor components.
Internal a/c compressor failure and system contamination often follows a leaking valve or indications of refrigerant venting from the valve. The cause of the valve opening condition should be found and repaired.
How to set the pressure relief valve on a car air compressor ?
The ac compressor pressure relief valve is calibrated by the manufacturer and there is no need to calibrate or repair. If the valve is leaking or faulty ,it should be replaced.
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