Service, Troubleshooting, and Efficiency

Understand that run capacitors improve efficiency and torque while start capacitors give a momentary starting boost and drop out.

Test capacitors against their microfarad rating and replace those reading well below spec.

Recognize that contactors switch line voltage to the compressor and fan and that residential control circuits operate at 24 volts.

Trace low evaporator airflow, from dirty filters, coils, or a weak blower, as a cause of a cold or frozen coil and low suction pressure.

Measure total external static pressure to identify restrictive ductwork.

Investigate compressor amp draw above rated load amps for high head pressure, low voltage, or failing windings.

Diagnose a silent outdoor unit on a cooling call as an electrical fault such as a failed contactor or open safety.

Trace furnace short cycling and flame loss to airflow limits, a dirty flame sensor, or oversizing.

Suspect a stuck reversing valve or failed solenoid when a heat pump blows cold air on a heat call.

Know SEER/SEER2 for cooling efficiency, AFUE for furnace efficiency, and HSPF/HSPF2 for heat-pump heating efficiency.

Perform routine maintenance such as filter changes, coil cleaning, and drain clearing to preserve airflow and efficiency.

Recognize ECM blowers as variable-speed, higher-efficiency alternatives to PSC motors.