Mitsubishi Electric CITY MULTI PUHY-P108 Service Handbook page 327

[ IX Troubleshooting ]
-2- Low-Pressure Sensor (63LS)
1. Compare the pressure that is detected by the low pressure sensor, and the low pressure gauge pressure
to check for failure.
Set the digital display switch (SW1) as shown below to display the pressure that is detected by the low pressure sensor on
the self-diagnosis LED.
(1) While the sensor is stopped, compare the gauge pressure and the pressure displayed on self-diagnosis LED1.
1) When the gauge pressure is between 0 and 0.098MPa [14psi], internal pressure is caused due to gas leak.
2) When the pressure displayed on self-diagnosis LED1 is between 0 and 0.098MPa [14psi], the connector may be
defective or be disconnected. Check the connector and go to (4).
3) When the pressure displayed on self-diagnosis LED1 exceeds 4.15MPa [14psi], go to (3).
4) If other than 1), 2) or 3), compare the pressures while the sensor is running. Go to (2).
(2) Compare the gauge pressure and the pressure displayed on self-diagnosis LED1 while the sensor is running.(Com-
pare them by MPa [psi] unit.)
1) When the difference between both pressures is within 0.03MPa [4psi], both the low pressure sensor and the main
board are normal.
2) When the difference between both pressures exceeds 0.03MPa [4psi], the low pressure sensor has a problem.
(performance deterioration)
3) When the pressure displayed on the self-diagnosis LED does not change, the low pressure sensor has a problem.
(3) Remove the low pressure sensor from the main board to check the pressure with the self-diagnosis LED display.
1) When the pressure displayed on the self-diagnosis LED is between 0 and 0.098MPa [14psi], the low pressure sen-
sor has a problem.
2) When the pressure displayed on self-diagnosis LED is approximately 1.7MPa [247psi], the main board has a prob-
lem.
When the outdoor temperature is 30°C [86°F] or less, the main board has a problem.
When the outdoor temperature exceeds 30°C [86°F], go to (5).
(4) Remove the low pressure sensor from the main board, and short-circuit between the No.2 and 3 connectors (63HS)
to check the pressure with the self-diagnosis LED.
1) When the pressure displayed on the self-diagnosis LED exceeds 1.7MPa [247psi], the low pressure sensor has a
problem.
2) If other than 1), the main board has a problem.
(5) Remove the high pressure sensor (63HS) from the main board, and insert it into the connector for the low pressure
sensor (63LS) to check the pressure with the self-diagnosis LED.
1) When the pressure displayed on the self-diagnosis LED exceeds 1.7MPa [247psi], the main board has a problem.
2) If other than 1), the main board has a problem.
2. Low-pressure pressure configuration
The low pressure sensor consists of the circuit shown in the figure below. If DC5V is applied between the red and the black
wires, voltage corresponding to the pressure between the white and the black wires will be output, and the value of this
voltage will be converted by the microcomputer. The output voltage is 0.173V per 0.098MPa [14psi].
∗The pressure sensor on the body side is designed to connect to the connector. The connector pin number on the body side
is different from that on the main board side.
Body side
Vcc Pin 1
Vout Pin 2
GND Pin 3
63LS
1 2 3
Connector
1 2 3 4 5 6 7 8 9 10
ON
Main board side
Pin 3
Pin 2
Pin 1
Pressure 0 ~ 1.7 MPa [247psi]
Vout 0.5 ~ 0.35 V
0.173 V / 0.098 MPa [14 psi]
1
GND (black)
2
Vout (White)
3
Vcc (DC 5 V)(Red)
- 318 -
1.8 [261]
1.6 [232]
1.4 [203]
1.2 [174]
1.0 [145]
0.8 [116]
0.6 [87]
0.4 [58]
0.2 [29]
0
0 0.5 1 1.5 2 2.5
Output voltage (V)
3 3.5