AirCompDXField reference for compressor & HVAC techs

HVAC Diagnose

Pick a symptom — get causes, checks, and fixes.

Cooling

AC running but not cooling Evaporator coil freezing / ice on lines Outdoor unit cool, indoor blowing warm

Compressor

Compressor hums then trips (won't start)Compressor short-cycles (on/off rapidly)Compressor loud / rattling / knocking

Heating / heat pump

Heat pump blowing cold air in heat mode Heat pump runs constantly in cold weather Outdoor coil iced solid — no defrost

Furnace / gas

Furnace won't ignite (HSI or spark)Furnace short-cycles on high-limit

Airflow

Weak airflow at supply registers Hot and cold rooms / uneven temperatures

Electrical

Outdoor unit trips breaker 24 V transformer keeps blowing / no low voltage

Refrigerant

High head pressure / unit cycling on HP Low suction pressure / high superheat

Controls / thermostat

Thermostat blank / no display Smart thermostat loses Wi-Fi

Condensate / drainage

Water leaking from air handler / ceiling stain

Ductless / mini-split

Mini-split flashing error / not running