Basic test procedure
13
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.
8.1.4 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:
1. High amperage.
2. Low refrigerant charge.
3. Frequent recycling.
4. Dirty condenser.
8.1.5 Terminal overload – Test (compressor external type)
1. Remove overload.
2. Allow time for overload to reset before attempting to test.
3. Apply ohmmeter probes to terminals on overload wires. There should be continuity
through the overload.
8.1.6 Terminal overload (internal)
Some model compressors are equipped with an internal overload. The overload is
embedded in the motor windings to sense the winding temperature and/or current draw.
The overload is connected in series with the common motor terminal.
Should the internal temperature and/or current draw become excessive; the contacts in the
overload will open, turning off the compressor? The overload will automatically reset, but
may require several hours before the heat is dissipated.
8.1.7 Checking the internal overload
1. With no power to unit, remove the leads from the compressor terminals.
2. Using an ohmmeter, test continuity between terminals C-S and C-R. If not continuous,
the compressor overload is open and the compressor must be replaced.
8.2 Sealed refrigeration system repairs
8.2.1 Equipment require
1. Voltmeter
2. Ammeter
3. Ohmmeter
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