Solenoid Valve - Mitsubishi Electric PU(H)Y-P250YGM-A Service Handbook

-3- Solenoid Valve

Check whether the output signal from the control board and the operation of the solenoid valve match.
Setting the self-diagnosis switch (SW1) as shown in the figure below causes the ON signal of each relay to be output to the
LED's.
Each LED shows whether the relays for the following parts are ON or OFF.
∗The circuits on some parts are closed when the relays are ON. Refer to the following instructions.
1 2 3 4 5 6 7 8 9 1 0
1 2 3 4 5 6 7 8 9 10
ON
1 2 3 4 5 6 7 8 9 10
ON
1 2 3 4 5 6 7 8 9 10
ON
When a valve malfunctions, check if the wrong solenoid valve coil is not attached the lead wire of the coil is not disconnected,
the connector on the board is not inserted wrongly, or the wire for the connector is not disconnected.
(1) In case of 21S4a (4-way switching valve)
About this 4-way valve
When not powered:
The electricity runs between the oil separator exit and the heat exchanger (in case of P500 model), between HEX1a and
2a (heat exchanger on the right (as you face the front of the unit)), and between the gas ball valve (BV1) and the accu-
mulator. This circulation is for cooling.
When powered:
The electricity runs between the oil separator and the gas ball valve, and between the heat exchanger and the accumu-
lator. This circulation is for heating.
Check the LED display and the intake and the discharge temperature for the 4-way valve to check whether the valve has
no faults and the electricity runs between where and where.Do not touch the pipe when checking the temperature, as the
pipe on the oil separator side will be hot.
∗Do not give an impact from outside, as the outer hull will be deformed leading to the malfunction of the inner valve.
(2) In case of 21S4b (4-way switching valve)
About this 4-way valve
When not powered:
The electricity runs between the oil separator exit and the heat exchanger (in the case of P500 model), and between
HEX1b and 2b (heat exchanger on the left (as you face the front of the unit)).
When powered:
The electricity runs between the heat exchanger and the accumulator, and the valve opens or closes the heat exchanger
circuit when cooling or heating.
Check the LED display and the switching sound to check whether the valve has no faults, however, it may be occasionally
difficult to check by the sound, as the switching coincides with 21S4a and 21S4b. In this case, check the intake and the
discharge temperature for the 4-way valve to check that the electricity runs between where and where.
∗Do not touch the valve when checking the temperature, as it will be hot.
∗Do not give an impact from outside, as the outer hull will be deformed leading to the malfunction of the inner valve.
(3) In case of 21S4c (4-way switching valve) (Only P500 model)
About this 4-way valve
When not powered:
The electricity runs between the oil separator exit and the heat exchanger (in the case of P500 model), and between
HEX1b and 2b (heat exchanger on the left (as you face the front of the unit)).
When powered:
The electricity runs between the heat exchanger and the accumulator, and the valve opens or closes the heat exchanger
circuit when cooling or heating.
Check the LED display and the switching sound to check whether the valve has no faults, however, it may be occasionally
difficult to check by the sound, as the switching coincides with 21S4a and 21S4c. In this case, check the intake and the
discharge temperature for the 4-way valve to check that the electricity runs between where and where.
∗Do not touch the valve when checking the temperature, as it will be hot.
∗Do not give an impact from outside, as the outer hull will be deformed leading to the malfunction of the inner valve.
SW1
LD1
21S4a
SV1
Display
LD2 LD3 LD4 LD5
21S4b 21S4c
CH11 CH12
SV3
SV5b SV5c
- 149 -
[ IX Troubleshooting ]
LD6 LD7 LD8
52F