Mitsubishi Electric PLA-A12BA Service Manual page 28

10-6-1. Thermistor
<Thermistor Characteristic graph>
Thermistor for
lower temperature
Thermistor R =15k
0
Fixed number of B=3480 ± 2%
t( )Rt=15exp { 3480(
0
10
20
25
30
40
10-6-2. DC Fan motor (FAN MOTOR/ INDOOR CONTROLLER BOARD)
Check method of DC fan motor (fan motor / indoor controller circuit board)
Notes
· High voltage is applied to the connecter (CNMF) for the fan motor. Give attention to the service.
· Do not pull out the connector (CNMF) for the motor with the power supply on.
(It causes trouble of the indoor controller circuit
Self check
Symptom : The indoor fan cannot turn around.
Check the fuse (FUSE) on indoor
controller board.
Did the fuse blow?
No
Wiring contact check
Contact of fan motor connector (CNMF)
Is there no contact failure?
Yes
Power supply check (Remove the connector (CNMF))
Measure the voltage in the indoor controller circuit
TEST POINT
: V (between 1 (+) and 4 (-) of the fan connector): V
DC
TEST POINT : V (between 5 (+) and 4 (-) of the fan connector): V
CC
Is the voltage normal?
No
Replace indoor
controller board.
Check the operation.
NG
Replace the fan motor.
Room temperature thermistor(TH1)
Pipe temperature thermistor/liquid(TH2)
Condenser/evaporator temperature
thermistor(TH5)
± 3%
1 1
) }
273+t 273
1 1
T-32
273+ 273
1.8
board and fan motor.)
Check the drain pump (DP).
Yes
Is the resistance between
terminals normal?
Replace drain pump (DP).
Wiring recovery
No
board.
Replace the fan motor.
Yes
Check the operation of fan.
Replace indoor controller board.
OK
END
50
40
30
20
10
0
Yes
No
DC294~325V
DC
DC15V
CC
Yes OK
END
NG
28
<Thermistor for lower temperature>
-20 -10 0 10 20 30 40 50
-4 -14 32 50 68 86 104122 F
Temperature
Replace indoor controller board (I.B).
Replace fan motor (MF).