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.