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COMPONENT OPERATION & TESTING
WARNING
DISCONNECT ELECTRICAL POWER TO
UNIT BEFORE SERVICING OR TESTING
COMPRESSORS
Compressors are single phase, 115 or 230/208 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 internally spring mounted and
externally mounted on rubber isolators.
COMPRESSOR WINDING TEST (See Figure 1)
Remove compressor terminal box cover and disconnect
wires from terminals. Using an ohmmeter, check
continuity across the following:
1. Terminal "C" and "S" - no continuity - open winding
- replace compressor.
2. Terminal "C" and "R" - no continuity - open winding
- replace compressor.
3. Terminal "R" and "S" - no continuity - open wind-
ing - replace compressor.
GROUND TEST
Use an ohmmeter 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.
Figure 2: Typical Ground Test
CHECKING 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.
THERMAL OVERLOAD (External)
Some compressors are equipped with an external
overload which is located in the compressor terminal
box adjacent to the compressor body (see Figure 3.)
Figure 1: Compressor Winding Test
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