Mitsubishi Electric City Multi CMH-WM250V-A, Service Handbook

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[8-5 Pressure Sensor Circuit Configuration and Troubleshooting Pressure Sensor Problems ]
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8-5-3 Comparing the Low-Pressure Sensor Measurement and Gauge Pressure
By configuring the digital display setting switch (SW4 (when SW6-10 is set to OFF)) as shown in the figure below, the pressure
as measured by the low-pressure sensor appears on the LED1 on the control board.
(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 1.7MPa [247psi], 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 sen-
sor is running. (Compare them by MPa [psi] unit.)
1) When the difference between both pressures is within 0.03MPa [4psi], both the low pressure sensor and the control board are normal.
2) When the difference between both pressures exceeds 0.03MPa [4psi], the low pressure sensor has a problem. (performance dete-
rioration)
3) When the pressure displayed on the self-diagnosis LED1 does not change, the low pressure sensor has a problem.
(3) Remove the low pressure sensor from the control board to check the pressure with the self-
diagnosis LED1 display.
1) When the pressure displayed on the self-diagnosis LED1 is between 0 and 0.098MPa [14psi], the low pressure sensor has a
problem.
2) When the pressure displayed on self-diagnosis LED1 is approximately 1.7MPa [247psi], the control board has a problem.

When the outdoor temperature is 30°C [86°F] or less, the control board has a problem.

When the outdoor temperature exceeds 30°C [86°F], go to (5).
(4) Remove the low pressure sensor from the control board, and short-circuit between the No.2
and 3 connectors (63LS:CN202) to check the pressure with the self-diagnosis LED1.
1) When the pressure displayed on the self-diagnosis LED1 exceeds 1.7MPa [247psi], the low pressure sensor has a problem.
2) If other than 1), the control board has a problem.
(5) Remove the high pressure sensor (63HS1) from the control board, and insert it into the connec-
tor for the low pressure sensor (63LS) to check the pressure with the self-diagnosis LED1.
1) When the pressure displayed on the self-diagnosis LED1 exceeds 1.7MPa [247psi], the control board has a problem.
2) If other than 1), the low-pressure sensor has a problem.
SW4
ON
1 2 3 4 5 6 7 8 9 10
ON
1 2 3 4 5 6 7 8 9 10
The figure at left shows that the switches 1 through 5 are set to ON and 6 through 10 are set to OFF.
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