Mitsubishi Electric MUZ-HJ25VA-E1 Service Manual page 28

H Check of R.V. coil
First of all, measure the resistance of R.V. coil to check if the coil is defective. Refer to 11-4.
In case CN721 is not connected or R.V. coil is open, voltage is generated between the terminal pins of the connector
although any signal is not being transmitted to R.V. coil.
Check if CN721 is connected.
Unit operates COOL mode even if it is set to HEAT mode.
Disconnect connector (CN61)
between the compressor and the
power module.
Turn ON the power supply and
press EMERGENCY OPERATION
switch once (COOL mode).
Unit operates HEAT mode even if it is set to COOL mode.
Disconnect connector (CN61)
between the compressor and the
power module.
Turn ON the power supply and press
EMERGENCY OPERATION switch
twice (HEAT mode).
I Check of outdoor fan motor
Check the resistance of fan motor. (Refer to
11-4.)
Disconnect the connector CN771 on the
inverter P.C. board.
Disconnect the connector (CN61) between
compressor and power transistor module.
Turn ON the power supply and press the
EMERGENCY OPERATION switch.
OBH648
Is there 230 VAC between CN721
on the inverter P.C. board 3 minutes
after the power supply is turned ON?
Replace the 4-way valve.
Is there 230 VAC between CN721
on the inverter P.C. board 3 minutes
after the power supply is turned ON?
Replace the 4-way valve.
Is the resistance of
No
fan motor normal?
Yes
Does the upper lamp of
OPERATION
INDICATOR lamp on
the indoor unit light up?
and
Yes
and
No
Replace the outdoor
fan motor.
After 3 minutes, is
there voltage 230 VAC
between CN771
on the inverter P.C.
board?
Yes
Replace the outdoor
fan motor.
28
Replace the inverter
No
P.C. board.
Replace the inverter
Yes
P.C. board.
Replace the inverter
and
No P.C. board.