Troubleshooting Flow - Mitsubishi Electric MUH-GA20VB-E1 Service Manual

11-3.
Trouble criterion of main parts
MUH-GA20VB MUH-GA25VB MUH-GA35VB
Part name
Measure the resistance with a tester.
Defrost
(Part temperature –10°C ~ 40°C)
thermistor
Refer to 11-5. "Test point diagram and voltage", "Outdoor deicer
(RT63)
P.C. board", the chart of thermistor.
Compressor
Measure the resistance between the terminals with a tester.
(MC)
(Coil wiring temperature –10°C ~ 40°C)
INNER
PROTECTOR
MUH-
-
GA20/GA25VB
E1
MUH-GA20VB-
150i 5°C OPEN
90i10°C CLOSE
C-R
MUH-
C-S
GA20/GA25VB -
E2
160i 5°C OPEN
90i10°C CLOSE
MUH-GA35VB
155i 5°C OPEN
90i10°C CLOSE
Measure the resistance between the terminals with a tester.
(Coil wiring temperature –10°C ~ 40°C)
Outdoor fan
motor
(MF)
INNER FUSE
145i 2°C
CUT OFF

11-4. Troubleshooting flow

Compressor and/or outdoor fan motor doesn't operate.
A A Check of outdoor unit
Start
Is the switch SW2-2 on the
indoor electronic control
P.C. board set to MUH type?
Operate the unit in COOL or HEAT mode by pressing the EMERGENCY OPERATION switch.
3-minute time delay works.
Test run operation operates for 30 minutes.
Compressor
doesn't operate.
Is there 5V DC between J205
the deicer P.C. board?
Is there 230V AC between 3 on the
compressor contactor (52C) and N
on the outdoor terminal block (TB1)?
Check the compressor and compressor
capacitor, and rectify the connecting wire.
Outdoor fan motor
doesn't operate.
Is there 5V DC between J205
the deicer P.C. board?
Check the outdoor fan motor
and rectify the connecting
wire.
Check method and criterion
MUH-GA20VB-
E1
3.41~4.18Ω 3.19~3.91Ω
5.41~6.63Ω 4.76~5.83Ω
Color of
lead wire
MUH-GA20VB
323 ~ 396 Ω
WHT-BLK
241 ~ 296 Ω
BLK-RED
Change the switch SW-2-2
No
on the indoor electronic control
P.C. board to MUH type.
Yes
No
+
–J101 – on
Yes
Replace the
No
deicer P.C.
board.
Yes
No
+
–J101 on
–
Yes
Normal
E2 MUH-GA25VB- MUH-GA25VB-
E1
2.99~3.67Ω 3.19~3.91Ω
4.02~4.92Ω 4.76~5.83Ω
Normal
MUH-GA25/GA35VB
Is there 230V AC between 4 on the
compressor contactor (52C) and
TAB20 on the deicer P.C. board?
Yes
Replace the
deicer P.C. board.
Is there 230V AC between 4 on the
compressor contactor (52C) and
TAB 20 on the deicer P.C. board?
Yes
Replace the
deicer P.C. board.
22
MUH-GA35VB
E2
2.46~3.01Ω
2.96~3.63Ω
189 ~ 233 Ω
270 ~ 332 Ω
Rectify the indoor and
outdoor connecting wire.
No
No
Is there 230V AC between L–N
on the outdoor terminal block (TB1)?
Yes
Rectify the connecting wire.
Rectify the indoor and
outdoor connecting wire.
No
No
Is there 230V AC between L–N on
the outdoor terminal block (TB1)?
Yes
Rectify the connecting wire.
Figure
WHT
C
P
AUX. MAIN
S
R
BLK
RED
MAIN
AUX.
FUSE
BLK RED WHT
P INNER PROTECTOR