Air Conditioner Error Codes Explained

May 25, 2026

When your air conditioner displays an error code, it's the system telling you exactly what's wrong. Understanding these codes can save you a service call — or at least help you describe the problem accurately when you do call a technician. Here's a guide to the most common AC error codes across major brands.

How to Read AC Error Codes

Error codes appear on the indoor unit's display panel or on the remote control screen. They typically consist of a letter and number (E1, F2, P4) or just a number. The meaning varies by brand, so always cross-reference with your owner's manual. That said, many codes follow common patterns across brands.

Common Error Code Categories

E Codes — Sensor & Communication Errors

Code	Common Meaning	DIY Fix?
E1	Indoor temperature sensor fault	Try resetting; replace sensor if persists
E2	Evaporator coil temperature sensor fault	Reset; call technician if persists
E3	Outdoor temperature sensor fault	Reset; call technician if persists
E4	Discharge temperature sensor fault	Call technician
E5	Communication error between indoor and outdoor unit	Check wiring connections; call technician
E6	Communication failure	Reset; call technician if persists

F Codes — Fan & Airflow Errors

Code	Common Meaning	DIY Fix?
F1	Indoor fan motor fault	Check for obstructions; call technician
F2	Outdoor fan motor fault	Check for debris; call technician
F3	Fan speed out of control	Call technician

P Codes — Protection & Safety Errors

Code	Common Meaning	DIY Fix?
P1	High voltage protection / power supply issue	Check power supply; call technician
P2	Low voltage protection	Check power supply; call technician
P4	Inverter module protection (overheating)	Clear outdoor unit; call technician
P5	Drain pump fault / water level protection	Clear drain line; check float switch

H Codes — Heating & Defrost Errors

Code	Common Meaning	DIY Fix?
H1	Defrost mode active (not an error — normal in heat mode)	Wait for defrost cycle to complete
H3	Compressor overload protection	Let unit cool; call technician if repeats
H5	IPM module protection	Call technician
H6	Motor position detection failure	Call technician

C / CH Codes — Common on LG Units

Code	Common Meaning	DIY Fix?
CH01	Indoor temperature sensor error	Reset; replace sensor if persists
CH02	Outdoor temperature sensor error	Reset; call technician
CH05	Communication error	Check wiring; call technician
CH10	Indoor fan motor locked	Check for obstructions; call technician
CH38	Outdoor unit error	Call technician

Brand-Specific Code References

Error code meanings vary significantly between brands. Here's where to find the correct reference for your unit:

Mitsubishi: Search "[model number] error codes" on Mitsubishi's support site
Daikin: Daikin's error codes are listed in the installation manual (different from the user manual)
LG: LG's ThinQ app often displays error code explanations directly
Samsung: Samsung's SmartThings app provides error code details for connected units
Carrier / Bryant: Error codes are in the service manual, available on the manufacturer's dealer portal

What to Do When an Error Code Appears

Note the code before resetting — it may disappear after a reset
Try a reset first: Turn off at the breaker, wait 30 seconds, restore power, wait 3 minutes, then restart. See our guide on how to reset your AC.
Check the obvious: Dirty filter, blocked outdoor unit, full drain pan
Look up the code in your owner's manual or the manufacturer's website
Call a technician if the code reappears after a reset or indicates a refrigerant, compressor, or electrical fault

Codes You Should Never Ignore

Any code indicating compressor fault or protection
Refrigerant pressure errors (high or low pressure codes)
Electrical protection codes (voltage, current, IPM module)
Communication errors that persist after reset

Error codes are your AC's way of asking for help. A quick reset fixes many temporary faults — but recurring codes always point to something that needs proper diagnosis and repair.

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