McQuay Air Conditioner Error Codes McQuay Air Conditioner Error Codes Error Codes Problem E1 Compressor 2 low pressure faulty E2 Compressor 2 excessive stress faulty E3 Compressor 2 overload E4 Indoor coil 2 Temp. sensor fault E5 System 2 leaving water Temp. 2 faulty F2 Indoor coil 1 Temp. sensor fault F4 Return air Temp. sensor fault F6 Communication faulty