Mitsubishi Electric PLA-SM71EA2 Service Manual page 27

9-6-1. Thermistor
<Thermistor Characteristic Graph>
Room temperature thermistor (TH1)
Thermistors for
Pipe temperature thermistor/liquid (TH2)
lower temperature
Condenser/evaporator temperature thermistor (TH5)
R : Thermistor resistance
t
t: Temperature
Thermistor R =15k" ± 3%
0
Fixed number of B=3480 ± 1%
1
{ (
R = R exp B
t 0
273 + t
t Rt
0: 15 k"
10: 9.6 k"
20: 6.3 k"
25: 5.4 k"
30: 4.3 k"
40: 3.0 k"
9-6-2. DC Fan motor (fan motor/indoor controller board)
Check method of DC fan motor (fan motor / indoor controller circuit board)
Notes
1
· 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 circuit
Self check
2
Symptom : The indoor fan cannot turn around.
Wiring contact check
The contact of fan motor connect (CNMF)
Is there contact failure? (loose connector, insert failure)
No
Power supply check (Without fan motor connected)
Remove the fan motor (Remove the fan motor connector CNMF) and measure the
voltage in the indoor controller circuit
TEST POINT
1 : V (between 1 (+) and 4 (−) of the fan motor connector): V
DC
TEST POINT 2 : V (between 5 (+) and 4 (−) of the fan motor connector): V
CC
Is the voltage normal?
No
OCH784
1
)}
-
273
board and fan motor.)
board.
Yes
Replace defective fan motor.
Note: If the indoor fan does not operate after replacing the
fan motor, also replace the indoor controller board.
Replace indoor controller board.
Note: If the indoor fan does not operate after replacing the
indoor controller board, also replace the fan motor.
Correct wiring.
280 V DC
DC
15 V DC
CC
27
< Thermistor for lower temperature >
50
40
30
20
10
0
-20 -10 0 10 20 30 40 50
Temperature (:)