Mitsubishi Electric MXZ-SM72TAM-U1 Service Manual page 58

4400 (U8): Fan trouble (Outdoor unit)
Abnormal points and detection methods
No rotational frequency is detected, a value outside the
specified range is detected during fan motor operation.
Diagnosis of failure
Check the fuse on the outdoor multi controller
circuit board.
Has the fuse melted?
Check the fan motor connector (CNF1 and
CNF2) for disconnection or looseness.
Is there any abnormality such as
disconnection, looseness or break-
age?
1. While the breaker is OFF, disconnect the compressor
wiring (U/V/W) from the outdoor power circuit board.
2. While the breaker is OFF, disconnect the fan motor con-
nector CNF1 and CNF2.
3. When 5 minutes have passed since turning ON the break-
er, turn SW7-1 ON.
4. Check the voltage of the outdoor multi controller circuit
board.
Test points are;
• VDC approx. 310 to 350 V DC (fan connector 1–4)
• VCC approx. 15 V DC (fan connector 5–4)
• VCC approx. 0–6.5 V DC (fan connector 6–4)
Is the voltage normal?
* For the detail, refer to "Check method of DC fan motor (fan motor/outdoor multi controller circuit board)".
Note:
• Set SW7-1 OFF after the troubleshooting completes.
• The fan sometimes starts on-off cycle operation during low-load operation or cooling at low outside temperature. It is not abnormal; the operation
ensures reliability of the product.
OCH800A_58
Yes
(Melted)
No
(Not melted)
Yes
No
No
Yes
Causes and checkpoints
• Malfunction of fan motor
• Disconnection of CNF connector
• Defective outdoor multi controller circuit board
Replace the outdoor multi controller circuit board.
Replace the defective fan motor.*
Connect the wiring/connector properly.
Replace it in the case of breakage.
Replace the outdoor multi controller circuit board
(Malfunction of thermistor circuit).
Replace the defective fan motor.