Mitsubishi Electric CITY MULTI PUHY-400YMF-B Service Handbook page 144

Symptom
4 "88" appears on re-
mote controller at the
registration and access
remote controller
Cause
[Generates at registration and confirmation]
1) Erroneous address of unit to be coupled.
2) Slipping off of transmission line of unit to be cou-
pled (No connection).
3) Faulty circuit board of unit to be coupled.
4) Installation miss of transmission line.
[Confirmation of different refrigerant system controller]
5) Breaking of power source of outdoor unit to be con-
firmed.
6) Slipping off 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 sup-
ply connector (CN40) is inserted into the central-
ized control transmission line of outdoor unit.
10) Short circuit of centralized control transmission
line.
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 DC 17 ~ 30 V
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 transmis-
sion line (TB7) of outdoor unit is not slipped off.
f) Confirm the voltage of centralized control
transmission line.
i) Normal in case of 10 V ~ 30 V
ii) Check the items 7) ~ 10) left in case that
other than i).
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