MXS Service Manual

Troubleshooting for Outdoor Unit SiUS121736EA
179 Service Diagnosis
7. Troubleshooting for Outdoor Unit
7.1 Refrigerant Shortage
Error Code U0
Outdoor Unit LED
Display
A j 1 h 2 h 3 i 4 i 5 h
Method of Error
Detection
Refrigerant shortage is detected by checking the input current value and the compressor running
frequency. If there is insufficient refrigerant, the input current tends to be lower than the normal
value.
Error Decision
Conditions
The following conditions continue for 7 minutes.
 Input current
≤ A × output frequency + B
 Output frequency > C
 If the error repeats, the system is shut down.
 Reset condition: Continuous run for about 60 minutes without any other error
Supposed
Causes
 Disconnection of the discharge pipe thermistor, indoor or outdoor heat exchanger thermistor,
room or outdoor temperature thermistor
 Closed stop valve
 Refrigerant shortage (refrigerant leakage)
 Poor compression performance of compressor
 Defective electronic expansion valve
A
(–) B (A) C (Hz)
18 class 10/1000 0.3 54
24/36 class 27/1000 2 40