Service & Maintenance / Extra Edition

Troubleshooting Challenge: A Heat Pump Compressor That’s Not Running

January 6, 2014
In this month’s troubleshooting problem, we have a customer who can only tell us that the equipment that serves their small office “isn’t working.” When you arrive, you confirm that the building temperature is far from the thermostat set point even though the indoor fan motor is operating normally and the return air filter is clean. Satisfied that the problem is not with the indoor section of the equipment, you move to the outdoor section. Noting the schematic diagram (click here for a PDF of the diagram), you use it to become familiar with the components and circuitry there.

When you evaluate the situation, you find the following:

1. The compressor is not running, and it is very hot.

2. The outdoor fan motor is very hot and attempting to operate.

3. Contacts 11 and 21, and 13 and 23 are closed.

Your next step in isolating this problem is to turn off the power supply and disconnect the appropriate wiring in order to check the following, with these results:

1. A digital meter test from C to H on the dual capacitor displays a series of random numbers, then all zeros, and then a series of random numbers again. (The data on the body of the capacitor shows that a C to H test should show 55 μF and a test from C to F should show 10 μF.)

2. A second test from C to F shows the same results as the C to H test.

Your troubleshooting question: What is the specific failure that is preventing this equipment from operating properly?

Compare your answer with ours by clicking on the PDF link below.

Publication date: 1/6/2014

PDF - January Troubleshooting Answer

For information on Jim Johnson’s HVACR technician training DVDs, go to

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