Mitsubishi Electric CAHV-R450YA-HPB Service Manual page 152

[ X Troubleshooting ]
Soleno id Valve
-3- Temperature sensor
Use the flowchart below to troubleshoot the temperature sensor.
Troubleshooting the thermistor
Start
Disconnect the thermistor to be checked from the circuit board.
Measure the actual temperature of the pipe at the thermistor.
Check the thermistor resistance.
Compare the actual temperature and the temperature that corresponds
to the thermistor resistance to see if there is a discrepancy between them.
No temperature difference
Yes
Connect the thermistor connector to the circuit board,
check the sensor reading according to the instructions
detailed in section 2 "Checking the sensor status,"
andcheck the temperature difference.
No temperature difference
Yes
Normal
* 1 The table below shows the thermistor numbers and their corresponding connectors.
Check each sensor by disconnecting the corresponding connector.
TH1 CN211 3-4
TH3 CN211 1-2
TH2 CN213 1-2
TH4 CN214 1-2
. Pull out the sensor connector from the control board.
* 2
Do not pull on the lead wire.
. Measure the resistance with a tester.
. If the measured value is within ± 10% of the value as shown in the table below, the circuit sensor is normal.
* 3 Use the dip switches and push switches to view the sensor reading on the LED.
(1) Low-temperature-range thermistor
: TH2,3,4,9,10,11,21
R
Thermistor
R = 15
50
40
30
20
10
0
-20 -10
HWE22020
*1
*2
No
Replace the thermistor.
*3
No
Check for proper connection.
Replace the control board.
TH9 CN990
1-2
TH10 CN192 3-4
TH11 CN192 1-2
TH21 CN212 3-4
= 15kohm ±3%
0
1
exp
{ 3385 (
t
273 +t 273
0 10 20 30 40 50
Temperature( °C )
(2) High-temperature-range thermistor: TH1
Thermistor
1
)}
110
100
- 143 -
R = 7.465kohm ±2%
120
R = 7.465
exp { 4057 (
t
90
80
70
60
50
40
30
20
10
0
40 50 60 70 80 90 100 110 120
Temperature( °C )
1 1
)}
273 +t 393
GB