Mitsubishi Electric CITY MULTI PUHY-P108 Service Handbook page 355

[ IX Troubleshooting ]
(6) Diode stack
Measure resistances between each pair of terminals on the diode stack with a tester, and use the results for troubleshoot-
ing.Refer to (5) " Intelligent power module (IPM) " for notes on measurement and tester selection.
Judgment value (reference)
+ (P)
- (N)
to (L1)
Red (-)
to (L2)
to (L3)
(7) Caution at replacement of inverter parts
1) Check for miswiring and loose connections.
Incorrect or loose wiring of such circuit components as IPM and diode stack may cause the IPM damage. Thor-
oughly check the wiring. Retighten all screws upon completion of all other work.
Connect the IPM control terminal carefully to the G/A board, as the terminal is very small.If the output wire from
the IPM to the compressor is connected incorrectly, the compressor will be damaged. Perform wiring carefully in
order of color shown in the wiring diagram below.
2) Coat the radiation surface of the IPM and diode stack evenly with the grease that is provided with the service parts.
Apply a thin layer of grease to the entire surface of the back of the IPM and diode stack, and screw the module
securely into place.
Wipe off any grease that may get on the wiring terminal to avoid terminal contact failure.
Black ( + )
+ (P) - (N) to (L1)
- - 5 - 200
ohm
- -
5 - 200 -
ohm
5 - 200 -
ohm
5 - 200 -
ohm
To compressor
Red White Black
U V W
N
G/A board
P
- 346 -
External view
to (L2) to (L3)
5 - 200 5 - 200
ohm ohm¹
- -
Internal circuit diagram
- -
- -
IPM
Blue
Capacitor
Black
L1 L2 L3
+
L1
L2
L3
-