Mitsubishi Electric CITY MULTI PUHY-P400YEM-A Service Handbook page 148

Symptom
4 "88" appears on re-
[Generates at registration and confirmation]
mote controller at
1) Erroneous address of unit to be coupled.
registration and
2) Disconnection of transmission line of unit to be
access remote
coupled (No connection).
controller
3) Faulty circuit board of unit to be coupled.
4) Installation miss of transmission line.
[Confirmation of different refrigerant system controller]
5) Disconnection of power source of outdoor unit to be
confirmed.
6) Disconnection of centralized control transmission
line (TB7) of outdoor unit.
7) Power supply connector (CN40) is not inserted into
centralized control transmission line in grouping
with different refrigerant system without using
MELANS.
8) More than 2 sets of power supply connector are
inserted into the centralized control transmission line
of outdoor unit.
9) In the system connected with MELANS, power
supply connector (CN40) is inserted into the
centralized control transmission line of outdoor unit.
10)Short circuit of centralized control transmission line
Cause
-145-
Checking method & countermeasure
a) Confirm the address of unit to be
coupled.
b) Check the connection of transmission
line.
c) Check the transmission terminal block
voltage of unit to be coupled.
i) Normal if voltage is DC17 ~ 30V
ii) Check the item d) in case other than i).
d) Confirm the power source of outdoor unit
to be coupled with the unit to be
confirmed.
e) Confirm that the centralized control
transmission line (TB7) of outdoor unit is
not disconnection.
f) Confirm the voltage of centralized control
transmission line.
i) Normal in case of 10V ~ 30V
ii) Check the items 7) ~ 10) left in case
other than i).