Mitsubishi Electric PQHY-P72ZLMU-A Service Handbook page 314

[ IX Troubleshooting ]
In the case of MA remote controller
2. Phenomena
When the remote controller operation SW is turned on, the operation status briefly appears on the display, then it goes off,
and the display lights out immediately, and the unit stops.
(1) Cause
1) The power for the M-NET transmission line is not supplied from the heat source unit.
2) Short circuit of the transmission line.
3) Incorrect wiring of the M-NETtransmission line on the heat source unit.
Disconnected wire for the MA remote controller or disconnected line to the terminal block.
The indoor transmission line is connected incorrectly to the transmission terminal block for centralized controller (TB7).
The male power supply connectors on the multiple heat source units are connected to the female power supply switch con-
nector (CN40).
In the system to which the power supply unit for transmission lines is connected, the male power supply connector is connect-
ed to the female power supply switch connector (CN40) on the heat source unit.
4) Disconnected M-NET transmission line on the indoor unit side.
5) Disconnected wire between the terminal block for M-NET line (TB5) of the indoor unit and the indoor unit board (CN2M) or
disconnected connector.
(2) Check method and remedy
1) When 2) and 3) above apply, check code 7102 will be displayed on the self-diagnosis LED on the heat source unit.
Same symptom for all units in a
system with one heat source
unit?
YES
Check the
self-diagnosis LED
Is the error code 7102
displayed?
NO
Check 1).
Refer to IX [4] -7- (2) "Troubleshooting transmission power circuit of heat source unit" for how to check item 1 in the flow chart
above.
HWE15150
NO
YES
Check for
2 and 3.
Correct the error.
- 305 -
Measure voltages of the
terminal block for transmission
line (TB5) on the indoor unit.
NO
17 - 30V?
Check 4.
YES
Check 5.
YES
Error found?
Correct
the error.
NO
Indoor unit board or
MA remote controller failure
GB