Mitsubishi Electric CITY MULTI PUHY-P108 Service Handbook page 358

(2) Troubleshooting transmission power circuit of outdoor unit
Check the voltage at the indoor/outdoor
transmission terminal block (TB3) of outdoor unit.
DC 24 ~ 30 V
Check the voltage at TB3 after removing transmission line from TB3.
DC 24 ~ 30 V
Check whether the male connector is connected to
the female power supply connector (CN40).
NO
Connected
Check voltage of terminal block for centralized control (TB7).
DC 24 ~ 30 V
Check voltage of TB7 by removing transmission line from TB7.
DC 24 ~ 30 V
Check the voltage between 1 and 2, and 1 and 3 of main board CNVCC1
DC 24 ~ 30 V
Check the voltage between 1 and 2, and 1 and 3 of main board CNVCC1
DC 24 ~ 30 V
Check if the connector (CNL1 and CNL2) on the
INV board are not disconnected.
Disconnected?
Check the voltage between 1 and 3 of INV board CNDC2.
DC 250 ~ 310 V
Check the voltage of the power supply terminal block (TB1).
AC 208 / 230 V
Check if the connector on the outdoor unit board
is not disconnected.
NV board
: CNDC2
Disconnected?
Check the wiring inside the outdoor unit.
G/A board: CNDC1 - INV board: CND2
Faulty wiring?
Check the fuse (F01) on the G/A board.
Broken?
Check the rush current protection resistor.
19 ~ 25
Check the diode stack.
Broken?
YES
Check whether the transmission line is disconnected, check
for contact failure, and repair the problem.
NO
YES
Check if the indoor/outdoor transmission line is not
short-circuited, and repair the problem.
NO
YES
YES
Check the wiring between connectors (CNS1 and TB3).
Check if the connector (CNS1) is not disconnected.
NO
Disconnected?
YES
NO
YES
Replace the main board.
NO
YES
Check and repair wiring between main board connector
(CNVCC1) and INV board connector (CNVCC1).
NO
YES
Connect it.
NO
YES
Replace the INV board.
NO
NO
Check and repair power source wiring and main power source.
YES
G/A board : CNDC1
YES
Connect it.
NO
YES
Repair wiring.
NO
YES
Replace the fuse.
NO
NO
Replace the rush current protection resistor.
YES
YES
Replace the diode stack.
NO
- 349 -
YES
Connect it.
NO
Check if the transmission line
for centralized control is not short-
circuited, and repair the problem.
Turn on the power again.
[ IX Troubleshooting ]