Mitsubishi Electric MUZ-GB50VA Service Manual page 32

MUZ-GB50VA-
E3
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
intelligent power module.
Turn ON the power supply and press
EMERGENCY OPERATION switch
twice (HEAT mode).
Unit operates HEAT mode even if it is set to COOL mode.
Disconnect connector (CN61)
between the compressor and the
intelligent power module.
Turn ON the power supply and
press EMERGENCY OPERATION
switch once (COOL mode).
Is there 230 VAC between CN721
on the inverter P.C. board 3 minutes
after the power supply is turned ON?
Yes
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?
No
Replace the 4-way valve.
32
and
Replace the inverter
No
P.C. board.
and
Replace the inverter
Yes P.C. board.