Midea PD Series Manual page 30

Terminal "R" and "S" - no continuity
- Open winding - replace compressor.
9.1.2 Ground test
Use an ohmmeter to set on its highest scale. Touch 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 2.) 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
9.1.4 Terminal overload (external)
Some compressors are equipped with an external overload which is located in the compressor terminal
box adjacent to the compressor body. The overload is wired in series with the common motor terminal.
The overload senses both major amperage and compressor temperature. High motor temperature or
amperage heats the disc causing it to open and break the circuit to the common motor terminal.
Heat generated within the compressor shell is usually due to:
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