Air Conditioners
Error codes, troubleshooting, and maintenance information for air conditioners.
Last updated: 2026-02-24
Error Codes
Failed indoor coil thermistor, Corroded sensor wire connections, Ice buildup encasing sensor, Control board sensor circuit failure
Failed outdoor coil thermistor, Weather damage to sensor wiring, Sensor displaced from coil surface, Control board sensor input failure
Compressor motor winding failure, Low refrigerant causing high discharge temperature, Dirty condenser coils restricting heat rejection, Electrical supply voltage out of range
Refrigerant leak at coil joints, Damaged refrigerant line from vibration, Corroded evaporator coil, Factory charge deficiency
Normal operation in low outdoor temperatures, Dirty outdoor coil causing excessive frost, Low refrigerant causing coil to freeze, Defrost timer or sensor initiating cycle
Filter runtime hours exceeded, Visible dust and debris accumulation on filter, Reduced airflow from outlet vents, Unit running longer cycles than normal
Maintenance
View all →Check the condensate drain line
Locate the condensate drain line (usually a PVC pipe near the indoor unit). Pour a cup of bleach or vinegar down the line to prevent algae and mold clogs. A clogged drain can cause water damage and trigger the system to shut off.
Clean the outdoor condenser unit
Turn off power to the unit. Remove debris (leaves, grass clippings) from around the unit and maintain 2 feet of clearance. Gently hose down the condenser fins from the inside out to remove dirt buildup. Do not use a pressure washer.
Replace or clean the air filter
Check the air filter monthly during heavy use seasons. Disposable filters should be replaced, while washable filters can be rinsed and dried. A dirty filter restricts airflow, reduces efficiency by up to 15%, and can freeze the evaporator coil.
Schedule professional maintenance
Have an HVAC technician inspect the system annually. They will check refrigerant levels, test electrical connections, inspect the evaporator and condenser coils, and verify thermostat calibration. Professional maintenance catches issues before they become expensive repairs.
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