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9. Basic test procedure
9.1 Defective compressor
Compressors are single phase, 220-240 volt, depending on the model unit. All compressor motors are permanent
split capacitor type using only a running capacitor across the start and run terminal.
All compressors are externally mounted on rubber isolators.
9.1.1 Compressor wiring test
Remove compressor terminal box cover and disconnect wires from terminals. Using an ohmmeter, check
continuity across the following:
Terminal "C" and "S" - no continuity: Open winding - replace compressor.
Terminal "C and "R" - no continuity: Open winding - replace compressor.
Terminal "R” and "S" - no continuity: Open winding - replace compressor.
9.1.2 Ground test
Use an ohmmeter set on its highest scale. Connect one lead to the compressor body (clean point of contact as a
good connection is a must) and the other probe in turn to each compressor terminal (see Figure below.) If a
reading is obtained, the compressor is grounded and must be replaced.
9.1.3 Checking the compressor efficiency
The reason for compressor inefficiency is normally due to broken or damaged suction and/or discharge
valves, reducing the ability of the compressor to pump refrigerant gas.
This condition can be checked as follows:
1. Install a piercing valve on the suction and discharge or liquid process tube.
2. Attach gauges to the high and low sides of the system.
3. Start the system and run a “cooling or heating performance test.”
If test shows:
A. Below normal high side pressure.
B. Above normal low side pressure.
C. Low temperature difference across coil.
The compressor valves are faulty - replace the compressor.
