Service Functions; Troubleshooting; Change In Defrost Setting; Pre-Heat Control Setting - Mitsubishi Electric Mr.Slim MUZ-GC25NA - C1 Service Manual

8

SERVICE FUNCTIONS

8-1. CHANGE IN DEFROST SETTING [MUZ-GC25/35 MUZ-GC50NA-
Changing defrosting finish temperature
<JS> When the JS wire of the outdoor Inverter P.C. board is cut/soldered, the defrost finish temperature is changed.
(Refer to 9-6.1.)
Jumper wire
Soldered
(Initial setting)
JS
None
(Cut)
8-2. PRE-HEAT CONTROL SETTING [MUZ-GC25/35 MUZ-GC50NA-
PRE-HEAT CONTROL
When moisture gets into the refrigerant cycle, it may interfere the start-up of the compressor at low outside tempera-
ture. The pre-heat control prevents this interference. The pre-heat control turns ON when outside temperature is 20°C
or below. When pre-heat control is turned ON, compressor is energized. (About 50 W)
<JK> When the JK wire of the inverter P.C. board is cut, pre-heat control is activated. (Refer to 9-6.1)
NOTE: When the inverter P.C. board is replaced, check the Jumper wires, and cut/solder them if necessary.
9

TROUBLESHOOTING

MUZ-GC25NA MUZ-GC35NA MUZ-GC50NA MUZ-GC60NA MUZ-GC71NA
9-1. CAUTIONS ON TROUBLESHOOTING
1. Before troubleshooting, check the following
1) Check the power supply voltage.
2) Check the indoor/outdoor connecting wire for miswiring.
2. Take care of the following during servicing
1) Before servicing the air conditioner, be sure to turn OFF the main unit first with the remote controller, and then after
confirming the horizontal vane is closed, turn OFF the breaker and/or disconnect the power plug.
2) Be sure to turn OFF the power supply before removing the front panel, the cabinet, the top panel, and the electronic
control P.C. board.
3) When removing the electrical parts, be careful to the residual voltage of smoothing capacitor.
4) When removing the electronic control P.C. board, hold the edge of the board with care NOT to apply stress on the
components.
5) When connecting or disconnecting the connectors, hold the housing of the connector. DO NOT pull the lead wires.
3. Troubleshooting procedure
1) First, check if the OPERATION INDICATOR lamp on the indoor unit is flashing on and off to indicate an abnormality.
To make sure, check how many times the abnormality indication is flashing on and off before starting service work.
2) Before servicing check that the connector and terminal are connected properly.
3) If the electronic control P.C. board is supposed to be defective, check the copper foil pattern for disconnection and
the components for bursting and discoloration.
4) Refer to 9-2. and 9-3.
Defrost fi nish temperature (°C)
MUZ-GC25/35 MUZ-GC50NA-
5
8
Lead wiring
]
C2
C2
9
18
]
C2
Housing point
24