Mitsubishi Electric City Multi PQHY-P72 Service Handbook page 268

Phenomena
4 "88" appears on the remote
controller when the address is
registered or confirmed.
An error occurs when the ad-
dress is registered or confirmed.
(common)
1. A wrong address is set to the unit
to be coupled.
2. The transmission line of the unit to
be coupled is disconnected or is
not connected.
3. Circuit board failure of the unit to
be coupled
4. Improper transmission line work
Generates at interlocking regis-
tration between LOSSNAY and
the indoor unit
5. The power of LOSSNAY is OFF.
Generates at confirmation of con-
trollers used in the system in
which the indoor units connected
to different heat source units are
grouped
6. The power of the heat source unit
to be confirmed has been cut off.
7. The transmission line for central-
ized control (TB7) is disconnect-
ed.
8. When the indoor units connected
to different heat source units are
grouped without MELANS, the
male power supply connector is
not connected to the female pow-
er supply switch connector
(CN40) for the transmission line
for centralized control.
9. The male power supply connec-
tors on 2 or more heat source
units are connected to the female
power supply switch connector
(CN40) for the transmission line
for centralized control.
10.In the system to which MELANS
is connected, the male power
supply connector is connected to
the female power supply switch
connector (CN40) for the trans-
mission line for centralized con-
trol.
11.Short circuit of the transmission
line for centralized control
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[ IX Troubleshooting ]
Cause
(1) Confirm the address of unit to be cou-
pled.
(2) Check the connection of transmission
line.
(3) Check voltage of the terminal block for
transmission line of the unit to be cou-
pled.
(i) Normal if voltage is between DC17
and 30V.
(ii) Check (4) in case other than i).
(4) Check for the main power of LOSSNAY.
(5) Check the power supply of the heat
source unit which is coupled with the
unit to be confirmed.
(6) Check that the transmission line for
centralized control (TB7) of the heat
source unit is not disconnected.
(7) Check voltage of the transmission line
for centralized control.
(i) Normal when voltage is between
10V and 30V
(ii) Check 8 - 11 described on the left in
case other than i).