Mitsubishi Electric MXZ-SM72TAM-U1 Service Manual page 46

1501 (U2): Closed valve in cooling mode
Abnormal points and detection methods
Stop valve is closed during cooling operation.
Both of the following temperature conditions have been
satisfied for 20 minutes or more during cooling operation.
TH22j−TH21j ≥ −3.6°F (−2°C)
TH23j−TH21j ≥ −3.6°F (−2°C)
Note:
• For indoor unit, the abnormality is detected if an operating unit satisfies
the condition.
Diagnosis of failure
Is the outdoor stop valve (liquid/gas)
fully open?
Disconnect the outdoor LEV wiring to check the
resistance.
Is the resistance detected?
OCH800A_46
No
Yes
No
Yes
Causes and checkpoints
• Outdoor liquid/gas valve is closed.
• Malfunction of outdoor LEV (LEV1) (blockage)
TH21:
Indoor intake temperature thermistor (RT11 or TH1)
TH22:
Indoor liquid pipe temperature thermistor (RT13 or TH2)
TH23:
Indoor gas pipe temperature thermistor (TH-A to E)
LEV:
Linear expansion valve
Open the outdoor stop valve (liquid/gas) fully.
Replace the outdoor LEV.
Replace the outdoor multi controller circuit
board.