Compressor HVAC: Testing and Inspection

1. Connect manifold gauge set.
2. Start and operate engine at fast idle. Check the following:
a. Ensure high pressure gauge reading is higher than low pressure reading and the the low pressure reading is not higher than normal.
b. Check for metallic sound.
c. Check compressor shaft seal for excessive gas or oil leakage. A slight amount of oil leakage from shaft seal is normal. If any malfunction is found, replace compressor.
3. False compressor seizure may occur after an extended period of disuse or storage. Use a clutch hub holding tool to turn compressor in opposite direction of rotation at least three revolutions. Check for false compressor seizure if compressor has not been used in a month or longer.
4. If compressor is not seized but will not rotate, check for current at magnetic coil. Low discharge pressure may be caused by faulty seals within the compressor, a restriction in the compressor or elsewhere, or by a low refrigerant charge. The compressor must have the correct amount of the proper viscosity oil. Excess oil will restrict refrigerant circulation and reduce compressor outlet pressure.