Mitsubishi Electric CITY MULTI PUHY-400YMF-B, Service Handbook

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TROUBLESHOOTING
[1] Principal Parts
(1) Judging Failure
Pressure Sensor (Discharge/Suction Pressure Sensor)
1) Check for failure by comparing the sensing pressure according to the high pressure/low pressure sensor and the
pressure gauge pressure.
Turn on switches 2, 4, 5, 6 (High) and 1, 2, 4, 5, 6 of the digital display select switch (MAIN board SW1) as shown
below, and the pressure sensor is displayed digitally by the light emitting diode LD1.
High Pressure Low pressure
1 In the stopped condition, compare the pressure readings from the gauge and from the LD1 display.
(a) If the gauge pressure is 0 ~ 1 kg/cm 2 G (0.098 MPa), the internal pressure is dropping due to gas leakage.
(b) If the pressure according to the LD1 display is 0 ~ 1 kg/cm 2 G (0.098 MPa), there is faulty contact at the connector,
or it is disconnected. Proceed to 4.
(c) If the pressure according to the LD1 display is 32 kg/cm 2 G (3.14 MPa) or higher, proceed to 3.
(d) If other than (a), (b) or (c), compare the pressure readings during operation. Proceed to 2.
2 Compare the pressure readings from the gauge and from the LD1 display while in the running condition.
(a) If the difference between the two pressures is within 1 kg/cm 2 G (0.098 MPa), both the affected pressure sensor
and the main MAIN board are normal.
(b) If the difference between the two pressures exceeds 1 kg/cm 2 G (0.098 MPa), the affected pressure sensor is faulty
(deteriorating performance).
(c) If the pressure reading in the LD1 display does not change, the affected pressure sensor is faulty.
3 Disconnect the pressure sensor from the MAIN board and check the pressure according to the LD1 display.
(a) If the pressure is 0 ~ 1 kg/cm
2
G (0.098 MPa) on the LD1 display, the affected pressure sensor is faulty.
(b) If the pressure is 32 kg/cm 2 G (3.14 MPa) or higher, the MAIN board is faulty.
4 Disconnect the pressure sensor from the MAIN board and short out the No. 2 and No. 3 pins of the connector (63HS),
then check the pressure by the LD1 display.
(a) If the pressure according to the LD1 display is 32 kg/cm 2 G (3.14 MPa) in the case of the low pressure sensor,
10 kg/cm
2
G (0.98 MPa) or higher, the affected pressure sensor is faulty.
(b) If other than (a), the MAIN board is faulty.
2) Pressure sensor configuration.
The pressure sensors are configured in the circuit shown in the figure at right. If DC 5 V is applied between the red and
black wires, a voltage corresponding to the voltage between the white and black wires is output and this voltage is
picked up by the microcomputer. Output voltages are as shown below.
High Pressure 0.1 V per 1 kg/cm 2 G
(0.098 MPa)
Low Pressure 0.3 V per 1 kg/cm 2 G
(0.098 MPa)
Connector
High pressure sensor;
Pressure 0 ~ 30 kg/cm
2
G
(0 ~ 2.9 MPa)
Vout 0.5 ~ 3.5 V
Low pressure sensor;
Pressure 0 ~ 10 kg/cm 2 G
(0 ~ 0.98 MPa)
Vout 0.5 ~ 3.5 V
GND (Black)
Vout (white)
Vcc (DC 5 V) (Red)
63HS/63LS
1 2 3 4 5 6 7 8 9 10
ON
1 2 3 4 5 6 7 8 9 10
ON