The equipment in this troubleshooting situation is a package unit heat pump and the customer’s complaint is that the unit is “blowing warm air.” When you respond to this service call, you confirm that the indoor temperature is near 90°F, and you also find that the customer has turned the equipment off while awaiting your arrival.

As your first step, you make sure that the thermostat is set to AUTO mode on the fan control, and initiate a cooling mode. After confirming that the indoor fan motor is operating normally, but blowing warm air, you begin a check of the electrical system (see the partial diagram in Figure 1) with a test of the heat/cool relay.

Your first test is at the coil of the relay, and your reading is 24 vac.

As your next test, you check at T1 on the contactor and terminal #4 on the heat/cool relay, and your meter shows 240 vac. A subsequent voltage test at T1 and terminal #2 on the relay shows 0 vac.

Your troubleshooting question: What is the next step you need to take in servicing this equipment?

Compare your answer with ours here.

Publication date: 7/4/2016

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