System Not Cooling

Check first:

• Thermostat settings and batteries
• Air filter — replace if dirty
• Circuit breakers — reset if tripped
• Outdoor unit — clear debris, check contactor

If still not cooling: Check refrigerant charge (superheat/subcooling), compressor operation, TXV function

System Not Heating

Check first:

• Thermostat set to HEAT mode
• Gas supply (furnaces) — pilot light, gas valve
• Heat pump — reversing valve operation
• Igniter and flame sensor (furnaces)

If still not heating: Check control board error codes, heat exchanger for cracks, heat pump refrigerant charge

Short Cycling

Common causes:

• Oversized equipment for the space
• Refrigerant overcharge or undercharge
• Dirty evaporator or condenser coil
• Low airflow — dirty filter, blocked registers
• Faulty thermostat or control board

Unusual Noises

Diagnose by sound:

• Banging: Loose parts, failing compressor
• Squealing: Belt or bearing issue
• Clicking: Relay/contactor issue
• Hissing: Refrigerant leak
• Rattling: Loose panels or debris

Water Leaks / Condensate Issues

Common causes:

• Clogged condensate drain line
• Dirty evaporator coil causing freeze/thaw
• Cracked or overflowing drain pan
• Condensate pump failure
• Refrigerant undercharge causing freeze-up

High Energy Bills

Common causes:

• Dirty air filter reducing airflow
• Refrigerant charge off (over or under)
• Dirty coils reducing heat transfer
• Duct leaks losing conditioned air
• Failing capacitor reducing motor efficiency