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Compressor Solenoid
A nominal 24-volt direct current coil activates the
internal compressor solenoid. The input control
circuit voltage must be 18 to 28 VAC. The coil
power requirement is 20 VAC. The external electrical
connection is made with a molded plug assembly.
This plug contains a full wave rectifier to supply direct
current to the unloader coil.
Compressor Solenoid Test Procedures
If it is suspected that the unloader is not working, the
following methods may be used to verify operation.
1. Operate the system and measure compressor
amperage. Cycle the compressor solenoid on
and off at 10-second intervals. The compressor
amperage should go up or down at least 25%.
2. If Step 1 does not give the expected results,
shut unit off. Apply 18 to 28 VAC to the solenoid
molded plug leads and listen for a click as the
solenoid pulls in. Remove power and listen for
another click as the solenoid returns to its original
position.
3. If clicks can't be heard, shut off power, remove the
control circuit molded plug from the compressor and
measure the solenoid coil resistance – 1640 ohms.
4. Next, check the molded plug.
Voltage Check: Apply control voltage to the plug
wires (18 to 28 VAC). The measured DC voltage
at the female connectors in the plug should be
around 15 to 27 VDC.
Resistance Check: Measure the resistance from
the end of one molded plug lead to either of the
two female connectors in the plug. One of the
connectors should read close to 0 ohms, while the
other should read infinity. Repeat with other wire.
The same female connector as before should read
zero, while the other connector again reads infinity.
Reverse polarity on the ohmmeter leads and repeat.
The female connector that read infinity previously
should now read close to 0 ohms.
Replace plug if either of these test methods does
not show the desired results.
FIGURE 78
Compressor Solenoid Location
Solenoid
Manual
Page
2100-749
55 of 68
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Troubleshooting
