Mitsubishi Electric CAHV-P500YB-HPB, Service Handbook

Page: 139 / 169

[
IX
Troubleshooting ]
- 132 -
HWE15070 GB
Solenoid 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.
No temperature difference
No
No
*2
*3
*1
Yes
Yes
No temperature difference
Normal
Compare the actual temperature and the temperature that corresponds
to the thermistor resistance to see if there is a discrepancy between them.
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.
Replace the thermistor.
Replace the control board.
Check for proper connection.
* 1 The table below shows the thermistor numbers and their corresponding connectors.
Check each sensor by disconnecting the corresponding connector.
TH1 . TH5 CN401
TH3 . TH7 CN402 3-4
TH2 . TH6 CN402 1-2
TH4 . TH8 CN404
TH9 CN405
TH16 . TH12 CN407 1-2
TH11 . TH13 CN407 3-4
* 2
. Pull out the sensor connector from the I/O board.
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)Thermistor <Heatsink temperature> :THHS
Resistance(kΩ)
Temperature(°C)
0
0 30 60 90 120
40
80
120
160
R = 17 kΩ±2%
50
R = 17
t
{4016( )}
273 +t
1
323
1
exp
Thermistor
(2) Low-temperature-range thermistor
: TH2,3,4,6,7,8,9,11,12,13,16
(3) High-temperature-range thermistor: TH1,TH5
Resistance
(kΩ)
Temperature(°C)
0
10
20
30
40
50
R = 15kΩ±3%
0
R = 15
t
{ 3385 ( )}
273 +t
1
273
1
exp
Thermistor
Resistance
(kΩ)
Temperature(°C)
R = 7.465kΩ ±2%
120
R = 7.465
t
{4057 ( )}
273 +t
1
393
1
exp
Thermistor
0
40 50 60 70 80 90 100 110 120
20
10
60
70
40
30
50
80
90
110
100
-20 -10 0 10 20 30 40 50
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