Mitsubishi MXZ-8B140VA Technical & Service Manual page 34

Abnormal point and detection method
Check code
Serial communication error
Abnormal if serial communication between
outdoor controller circuit board and
outdoor power circuit board is defective.
Ed
(0403)
Forced compressor stop.
(Overlap malfunction of drain pump in
indoor unit and linear expansion valve in
branch box.)
PA
(2520)
When condition of the outdoor unit is
forcefully stopped, which means the
drain sensor detects continuously to go
under water 5 times, and also detects
"[liquid pipe temperature - suction
temperature] [ – 10deg" for 30 minutes
continuously, the indoor unit and indoor
units in same refrigerant system which
operates in cooling, heating or dry mode
stops abnormally. Also, the outdoor unit
which is connected to that indoor unit
with refrigerant system stops abnormally
(compressor is suspended to operate). In
this time, <PA> is displayed.
OCH480D
Case
1 Breaking of wire or contact
failure of connector CN2
between the outdoor controller
circuit board and the outdoor
power circuit board
2 Breaking of wire or contact
failure of connector CN4
between the outdoor controller
circuit board and the outdoor
power circuit board
3 Defective communication circuit
of outdoor power circuit board
4 Defective communication circuit
of outdoor controller circuit board
for outdoor power circuit board
1 Drain pump trouble
2 Drain defective
· Drain pump clogging
· Drain pipe clogging
3 Open circuit of drain sensor
side heater
4 Contact failure of drain sensor
connector
5 Dew condensation on drain
sensor
· Drain water descends along
lead wire.
· Drain water waving due to filter
clogging
6 Indoor controller board defective
· Drain pump drive circuit failure
· Drain heater output circuit failure
7 Both of above mentioned 1–6
and the linear expansion valve
full closed failure happens
synchronistically.
34
Judgment and action
12 Check connection of each connector CN2
and CN4 between the outdoor controller
circuit board and the outdoor power circuit
board.
3 Replace outdoor power circuit board.
4 Replace outdoor controller circuit board.
1 Check the drain pump.
2 Please confirm whether water can be
drained.
3 Confirm the resistance of the drain sensor
side heater.
4 Check the connector contact failure.
5 Check the drain sensor leadwire mounted.
Check the filter clogging.
6 If the above mentioned checkpoints has any
problem, replace the indoor controller board.
7 Check whether the indoor linear expansion
valve leaks or not.