Mitsubishi Electric Mr.SLIM PCA Series Service Manual page 25

9-6-1. Thermistor
<Thermistor Characteristic graph>
Room temperature thermistor (TH1)
Thermistor for
Pipe temperature thermistor/liquid (TH2)
lower temperature
Condenser/evaporator temperature thermistor (TH5)
Thermistor R =15k ± 3%
0
Fixed number of B=3480 ± 2%
1
t( )Rt=15exp { 3480(
273+t
273+
0
10
20
25
30
40
9-6-2. DC Fan motor (fan motor/indoor controller circuit 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. Pay 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.
Wiring contact check
Contact of fan motor connector (CNMF)
Yes
Is the fuse blown?
No
Is there contact failure?
No
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?
Yes
Sensor signal check
Measure the voltage between CNMF
and DC 15V in the indoor controller circuit board.
Does the voltage repeat
DC 0V and DC 15V?
Yes
Replace the indoor
controller board.
OK
Check the operation
NG
Replace the fan motor.
OCH501
1
) }
273
1 1
T-32
273
1.8
board and fan motor.)
Is the resistance between
terminals of drain pump is normal?
(When the drain pump (option)
is connected)
No
Replace the drain pump.
Wiring recovery
Yes
board.
DC294~325V
DC
DC15V
CC
No Indoor controller board fuse check
and DC 0V
No
Replace the fan motor.
Check the operation of fan.
Replace the indoor controller board.
END
<Thermistor for lower temperature>
50
40
30
20
10
0
-20 -10 0 10 20 30 40 50
-4 -14 32 50 68 86 104122 °F
Yes
Replace the indoor controller board.
Replace the fan motor.
Yes OK
END
NG
25
°C
Temperature