Mitsubishi Electric City Multi PQHY-P72 Service Handbook page 299

[ 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
[1] Perform the following:
Check the com- Remove the connector
pressor INV (CNDR2) on the compressor
board error de- INV board.
tection circuit. 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.)
[2] Disconnect the compressor wir-
Check for com- ing, and check the compressor
pressor ground Meg, and coil resistance.
fault or coil er-
ror.
Items to be checked
1) IPM/overcurrent breaker
2) Logic error
3) ACCT sensor circuit fail-
4) DCCT sensor circuit fail-
5) IMP open (530 Detail
1) Compressor Meg failure
2) Compressor coil resis-
- 290 -
Phenomena
Replace the compressor INV
trip board.
(4250 Detail code No.
101, 102, 103, 104, 105,
106, and 107)
Replace the compressor INV
(4250 Detail code No. board.
111)
Check the resistance of the current
ure sensor ACCT referring to
(5301 Detail code 9.[4].8.(4) "Current Sensor ACCT",
No.115) and replace the sensor when ab-
normal.
Replace the compressor INV
board if the ACCT is normal.
Replace the DCCT sensor.
ure After replacing the DCCT, operate
(5301 Detail code the outdoor(heat source) unit
No.116) again.In the case when the error
occurs again, replace the com-
pressor INV board. (The DCCT
may be normal.)
Normal
code No.119)
Replace the compressor
Error if less than 1 Mohm. Check that no liquid refrigerant in
When no liquid refrigerant the compressor.
in the compressor
tance failure
Coil resistance value of
0.16 ohm (20°C [68°F)
Remedy