Mitsubishi Electric City Multi PQHY-P72 Service Handbook page 265

[ IX Troubleshooting ]
(2) In case of M-NET remote controller
Phenomena
1 Even if the operation button on
the remote controller is
pressed, the display remains
unlit and the unit does not start
running.
(Power indicator
appear on the screen.)
Cause
1. The power for the M-NET trans-
mission line is not supplied from
the heat source unit.
2. Short circuit of the transmission
line.
does not 3. Incorrect wiring of the M-NET
transmission line on the heat
source unit.
Disconnected wire for the MA re-
mote controller or disconnected
line to the terminal block.
The indoor transmission line is
connected incorrectly to the
transmission terminal block for
centralized controller (TB7).
4. Disconnected transmission line
on the remote controller.
5. Remote controller failure
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Check method and remedy
Check voltage of the transmission terminal
block for of the M-NET remote controller.
(1) If voltage between is 17V and 30V
-> M-NET remote controller failure
(2) When voltage is 17V or less
-> Refer to 9. [4].7.(2) "Heat source unit
transmission power source circuit
failure judgment".
When 2. and 3. apply, check code 7102
will be displayed on the self-diagnosis
LED.