Mitsubishi Electric PSA Series Service Manual page 24

9-5-1. Thermistor
<Thermistor characteristic graph>
Thermistor for
lower temperature
Thermistor R =15 k" ± 3%
0
Fixed number of B=3480 ± 2%
1
Rt=15exp { 3480(
273+t
0°C 15 kΩ
10°C 9.6 kΩ
20°C 6.3 kΩ
25°C 5.4 kΩ
30°C 4.3 kΩ
40°C 3.0 kΩ
9-5-2. DC Fan motor (FAN MOTOR/INDOOR CONTROLLER BOARD)
Check method of DC fan motor (fan motor/indoor controller board)
1. Notes
· High voltage is applied to the connector (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 board and fan motor.)
2. Self check
Symptom: The indoor fan cannot rotate.
Indoor controller board fuse check
Is the fuse normal?
Yes
Wiring contact check
Contact of fan motor connector (CNMF)
Is there contact failure?
No
Power supply check (Remove the connector (CNMF))
Measure the voltage in the indoor controller board.
TEST POINT 1: V (between 1 (+) and 4 (−) of the fan connector): V
DC
TEST POINT 2: V (between 5 (+) and 4 (−) of the fan connector): V
CC
Is the voltage normal?
No
Replace the indoor
controller board.
Check the operation.
Fail
Replace the defective fan motor.
OCH724
Room temperature thermistor (TH1)
Pipe temperature thermistor (TH2)
Condenser/evaporator temperature thermistor (TH5)
1
) }
273
No
Is the resistance between the terminals
of LOUVER MOTOR normal?
Replace the LOUVER MOTOR.
Replace the fuse.
Yes
Correct the wiring.
Yes
OK
Complete.
< Thermistor for lower temperature >
50
40
30
20
10
0
-20 -10 0
Yes
No
310-340 V DC
DC
15 V DC
CC
Replace the defective fan motor.
Check the operation of fan.
Fail
Replace the indoor controller board.
24
10 20 30 40 50
Temperature (:)
Replace the defective fan motor.
Replace the indoor controller board.
OK
Complete.