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Air Conditioner Error Codes by Brand

Air conditioner and heat pump codes cover airflow, sensors, drainage and communication between the indoor and outdoor units. Homeowners can safely handle filters, power resets and drainage checks; refrigerant and electrical work needs a licensed technician.

Choose your brand

• Daikin20 codes
• Fujitsu20 codes
• LG13 codes
• Mitsubishi Electric18 codes
• Samsung17 codes

Common air conditioner codes

• U4Daikin: Indoor and outdoor units can't communicate
• U0Daikin: Low refrigerant or restricted refrigerant flow
• 11Fujitsu: Indoor and outdoor units can't communicate
• 12Fujitsu: Wired remote controller communication error
• CH05LG: Indoor and outdoor units aren't communicating
• CH01 / CH02 / CH06LG: Temperature sensor fault
• Blinking OPERATION lightMitsubishi Electric: Wall unit's indicator light is flashing
• P1Mitsubishi Electric: Room air temperature sensor fault
• CFSamsung: Filter cleaning reminder
• ClSamsung: Auto Clean running

First checks for any air conditioner code

• Note the exact code and your model number before anything else.
• Unplug the air conditioner or switch off its breaker for 10 minutes, then try again. Many codes are one-off glitches.
• Clean or replace the air filter first. A dirty filter causes many airflow and freezing codes.
• Never open refrigerant lines or electrical panels. Those are jobs for a licensed HVAC technician.

Our air conditioner guides cover 88 codes across 5 brands. Each one explains the code in plain English, lists safe steps in order, and says clearly when to call a professional.