Figure 1. Indoor airflow system evaluation results.
Figure 1. Indoor airflow system evaluation results.

This troubleshooting situation centers around an older 3-ton split comfort cooling system, and the customer is calling because their home is “just not comfortable.” The homeowner also tells the dispatcher that while the unit is operating and air is coming out of the registers, the temperature in the house is too warm, and the system seems to be running constantly. The homeowner also mentions that they replaced the filter, but it didn’t seem to make any difference.

When you arrive, you confirm that the air handler is running, and although the thermostat setpoint is 75°F, the indoor temperature is too warm. Moving to the outdoor unit, you find that the compressor and outdoor fan motor are operating normally, and that the condenser coil is clean. When you confirm the outdoor ambient temperature and check the suction and discharge pressures of the system, you get the results shown in Figure 1.

Based on the refrigerant pressures shown, and information from the customer that they have never had any maintenance performed on the equipment, you decide to perform an indoor airflow system evaluation, and the results you find are shown in the illustration.

Your two-part troubleshooting question:

1. What is your next step in servicing this equipment?

2. What specific test results led you to your conclusion?

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

Publication date: 3/9/2015

PDF - March Troubleshooting Answer

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

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