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_TROUBLE SHOOTING GUIDE BOOK _
9. Temperature Sensor
■ Checking Method (Flow Chart)
1. Check the condition of installation and the contact of temperature sensor.
2. Check whether the connector contact of temperature sensor is normal.
3. Measure the resistance of temperature sensor.
TH1 TH2 TH3
Resistance
10KΩ±1%(25℃) 5KΩ±1%(25℃) 200KΩ±1%(25℃)
1.07KΩ±3.3%(85℃) 535KΩ±3.3%(85℃) 28KΩ±7.7%(85℃)
* TH1 : Outdoor temperature sensor
* TH2 : Pipe temperature sensor
* TH3 : Discharge pipe(D-pipe) temperature sensor
After power supplied,
the temperature on LGMV
is normal before
operating?
The output is normal?
1. Check the connector location
and the connecting direction
2. Check the contact failure
PCB checking and replacement
Replace the temperature sensor
Checking start
No malfunction of temperature
sensor
Yes
Yes
No
No
10. Pressure(High/Low) Sensor
Connect manifold gauge to the service valve of outdoor unit, and compare the output of high pressure
sensor to the output of low pressure sensor to detect the defect.
below) Compare the output of pressure sensor to the output of manifold gauge pressure using the table
below.
Read the pressure clearly between black and white as the composition of pressure sensor.
<Low Pressure Sensor> <High Pressure Sensor>
1) If the pressure of manifold gauge is 0~1kg/cm
2
, it indicates the pressure got lower due to the leak-
age of refrigerant. Find the place of leakage and fix it.
2) If the difference of the outputs of high and low pressure is in the range of 1kg/cm2, the pressure
sensor is normal.
3) If the difference of the outputs of high and low pressure is over 1kg/cm2, the pressure sensor is out
of order, it need to be replaced.
4) The composition of pressure sensor
The pressure sensor is composed like the circuit picture shown above. If DC 5V voltage flows on red
and black wire, voltage would be made between the white and black wire. The pressure which is
equivalent to the pressure output is shown in the table above.
- 67 -
Copyright ©2011 LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only
Checking Method for Key Components
Connect manifold gauge to the service valve of outdoor unit, and compare the output of high pressure sensor to
the output of low pressure sensor to detect the defect.
below) Compare the output of pressure sensor to the output of manifold gauge pressure using the table below.
Read the pressure clearly between black and white as the composition of pressure sensor.
1) If the pressure of manifold gauge is 0~1kg/cm
2
, it indicates the pressure got lower due to the leakage of refriger-
ant. Find the place of leakage and fix it.
2)
If the difference of the outputs of high and low pressure is in the range of 1kg/
cm
2
, the pressure sensor is normal.
3) If the difference of the outputs of high and low pressure is over 1kg/cm
2
, the pressure sensor is out of order, it
need to be replaced.
4) The composition of pressure sensor
The pressure sensor is composed like the circuit picture shown above. If DC 5V voltage flows on red and black
wire, voltage would be made between the white and black wire. The pressure which is equivalent to the pressure
output is shown in the table above.
1) The outdoor fan is controlled by the inverter motor which can control the number of rotations.
2) The outdoor fan is controlled by the high/low pressure of the outdoor unit after the operation of compressor.
3) There is possibility that the outdoor fan does not operate due to low capacity operation or low outdoor tempera-
ture even if the compressor is operating. This does not mean breakdown of the unit, the fan will start operating if
it reaches the set point.
2.8 Pressure Sensor(High/Low Pressure Sensor)
2.9 Outdoor Fan
<Low Pressure Sensor> <High Pressure Sensor>
OUTPUT CHARACTERISTICSOUTPUT CHARACTERISTICS
High Pressure Sensor : 0~5MPa
Vout 0.5~3.5V
Low Pressure Sensor : 0~2MPa
Vout 0.5~3.5V
(Red)
(Black)
(White)
±5%
Pressure
sensor
- 67 -
Copyright ©2011 LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only
Checking Method for Key Components
Connect manifold gauge to the service valve of outdoor unit, and compare the output of high pressure sensor to
the output of low pressure sensor to detect the defect.
below) Compare the output of pressure sensor to the output of manifold gauge pressure using the table below.
Read the pressure clearly between black and white as the composition of pressure sensor.
1) If the pressure of manifold gauge is 0~1kg/cm
2
, it indicates the pressure got lower due to the leakage of refriger-
ant. Find the place of leakage and fix it.
2)
If the difference of the outputs of high and low pressure is in the range of 1kg/
cm
2
, the pressure sensor is normal.
3) If the difference of the outputs of high and low pressure is over 1kg/cm
2
, the pressure sensor is out of order, it
need to be replaced.
4) The composition of pressure sensor
The pressure sensor is composed like the circuit picture shown above. If DC 5V voltage flows on red and black
wire, voltage would be made between the white and black wire. The pressure which is equivalent to the pressure
output is shown in the table above.
1) The outdoor fan is controlled by the inverter motor which can control the number of rotations.
2) The outdoor fan is controlled by the high/low pressure of the outdoor unit after the operation of compressor.
3) There is possibility that the outdoor fan does not operate due to low capacity operation or low outdoor tempera-
ture even if the compressor is operating. This does not mean breakdown of the unit, the fan will start operating if
it reaches the set point.
2.8 Pressure Sensor(High/Low Pressure Sensor)
2.9 Outdoor Fan
<Low Pressure Sensor> <High Pressure Sensor>
OUTPUT CHARACTERISTICSOUTPUT CHARACTERISTICS
High Pressure Sensor : 0~5MPa
Vout 0.5~3.5V
Low Pressure Sensor : 0~2MPa
Vout 0.5~3.5V
(Red)
(Black)
(White)
±5%
Pressure
sensor
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