Daikin AT12BV1LS Pocket Manual page 59

Troubleshooting
5.2.16 Four Way Valve Abnormality
Remote
Controller
Display
Method of
Malfunction
Detection
Malfunction
Decision
Conditions
Supposed
Causes
58
EA
The liquid pipe temperature thermistor, the outdoor air
temperature thermistor and the outdoor unit heat
exchanger thermistor are checked to see if they function
within their normal ranges in the operating mode.
A following condition occurs after 3 minutes of the
compressor start.
Cooling / dry operation
(outdoor unit heat exchanger temp. – liquid pipe
temp.) < –5°C
Heating
(liquid pipe temp. – outdoor unit heat exchanger
temp.) < 0°C
Connector in poor contact
Thermistor defective
Outdoor unit PCB defective
Four way valve coil or harness defective
Four way valve defective
Foreign substance mixed in refrigerant
Insufficient gas
Si10-417
Service Diagnosis