Mitsubishi Electric City Multi CMB-P1016NU-G, Service Handbook

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[
IX
Troubleshooting ]
Note:
1. Due to a large capacity electrolytic capacitor used in the inverter, voltage still flows through even after the unit is turned off,
which may cause electric shock.As a result, wait for a sufficient length of time (5~10 minutes) after the main power is turned
off, and check the voltage drop at both terminals of the electrolytic condensers.
2. The components of the inverter such as IPM will be damaged if the screws for inverter wiring are not tightened tightly or the
connectors are not properly inserted.When an error occurs after the components are replaced, the wrong wiring is the cause
in most cases. Check that the wiring is correct, the screws are not loosely tightened, and the connectors and Faston are
not loosely inserted.
3. Do not remove or insert inverter connectors with the main power supply on, as this will result in damage to the PCB.
4. The electric current sensor will be damaged if current flows without the control board being connected.Always insert con-
nectors into the corresponding PCB when running the inverter.
(2) Inverter output related troubles
Items to be checked Phenomena Remedy
[1]
Check the com-
pressor INV
board error de-
tection circuit. Perform the following:
Remove the connector
(CNDR2) on the compressor
INV board.
Operate the outdoor(heat
source) unit after above steps.
Check the error status.
(The compressor does not run
because CNDR2, which out-
puts the IPM drive signal, has
been disconnected.)
1) IPM/overcurrent breaker
trip
(4250 Detail code No.
101, 102, 103, 104, 105,
106, and 107)
Replace the compressor INV
board.
2) Logic error
(4250 Detail code No.
111)
Replace the compressor INV
board.
3) ACCT sensor circuit fail-
ure
(5301 Detail code
No.115)
Check the resistance of the current
sensor ACCT referring to
9.[4].8.(4) "Current Sensor ACCT",
and replace the sensor when ab-
normal.
Replace the compressor INV
board if the ACCT is normal.
4) DCCT sensor circuit fail-
ure
(5301 Detail code
No.116)
Replace the DCCT sensor.
After replacing the DCCT, operate
the outdoor(heat source) unit
again.In the case when the error
occurs again, replace the com-
pressor INV board. (The DCCT
may be normal.)
5) IMP open (530 Detail
code No.119)
Normal
[2]
Check for com-
pressor ground
fault or coil er-
ror. Disconnect the compressor wir-
ing, and check the compressor
Meg, and coil resistance. 1) Compressor Meg failure
Error if less than 1 Mohm.
When no liquid refrigerant
in the compressor
2) Compressor coil resis-
tance failure
Coil resistance value of
0.16 ohm (20°C [68°F)
Replace the compressor
Check that no liquid refrigerant in
the compressor.