Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Compressor Discharge Switch
This switch is incorporated into the system to provide compressor shut-off when it senses low refrigerant pressure. The switch is located in the evaporator inlet line (high pressure) and is wired in series between the compressor clutch and the master switch on the control. When low pressure is detected, the switch breaks contact with the circuit, thus shutting off the system and preventing compressor failure or seizure.
This switch also performs the function of an ambient temperature switch, since the pressure at the switch varies directly with ambient temperatures. The compressor should not run below 25°F ambient temperature or 37 psi at the switch. The compressor should run in A/C modes above 45°F ambient temperature or 42 psi at the switch.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.