Mitsubishi Electric City Multi PQHY-P72 Service Handbook page 267

[ IX Troubleshooting ]
Phenomena
3 "HO" or "PLEASE WAIT" dis-
play on the remote controller
does not disappear, and no op-
eration is performed even if the
button is pressed.
Check method and remedy
Without using MELANS
Are all the units in the system
experiencing the same problem?
Check the address of
the heat source unit.
51 - 100?
Check the centralized centralized
switch (SW2-1) on the heat source unit.
Heat source unit main
board failure
*1. When the heat source unit address is set to 1 - 50, the address will be forcibly set to 100.
Using MELANS
When MELANS is used, "HO" or "PLEASE WAIT" display on the remote controller will disappear when the indoor unit and the local
remote controller (M-NET remote controller) are grouped.
If "HO" or "PLEASE WAIT" does not disappear after the registration, check the 11. - 13.
Without using MELANS
1. Heat source unit address is set to "00"
2. A wrong address is set.
A wrong address is set to the indoor unit to be coupled with the remote controller.
100 must be subtracted from the address of the M-NET remote controller.
A wrong address is set to the M-NET remote controller
(100 must be added to the address of the indoor unit.)
3. Faulty wiring of the terminal block for transmission line (TB5) of the indoor unit in the same group
with the remote controller.
4. The centralized control switch (SW2-1) on the heat source unit is set to ON.
5. Disconnection or faulty wiring of indoor unit transmission line.
6. Disconnection between the terminal block for M-NET line connection (TB5) of the indoor unit and
the male connector (CN2M)
7. The male power supply connectors on 2 or more heat source units are connected to the female
power supply switch connector (CN40) for the transmission line for centralized control.
8. Heat source unit main board failure
9. Indoor unit board failure
10.Remote controller failure
Interlocking control with MELANS
11.No group registration is made using MELANS. (The indoor unit and the M-NET remote controller
are not grouped.)
12.Disconnected transmission line for centralized control (TB7) of the heat source unit
13.In the system to which the power supply unit for transmission lines is connected, the male power
supply connector is connected to the female power supply switch connector (CN40) on the heat
source unit
NO
YES
*1
NO
A wrong address is set
to the heat source unit.
YES
YES
Wrong switch setting
ON?
Change it from
ON to OFF.
NO
Cause
NO
A wrong address is
set to the M-NET
remote controller.
NO
A wrong address is
set to the indoor unit.
Wrong wiring of the
NO
M-NET transmission
line of the indoor unit
YES
Disconnected
connector (CN2M)
Correct
the error.
- 258 -
Check the address of the M-NET remote
controller on which "HO" is displayed.
Indoor unit + 100?
YES
Check the address of the
indoor unit to be coupled.
M-NET remote controller
- 100?
YES
Measure voltages of the terminal
block for transmission line (TB5)
on the indoor unit.
17 - 30V?
YES
Check connection between indoor M-NET
transmission terminal block (TB5) and the
male connector (CN2M)
Disconnected?
NO
Indoor unit board or
remote controller failure