Mitsubishi Electric CITY MULTI PUHY-P108 Service Handbook page 328

-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.
SW1
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 P126 - P144 model) HEXB, between
heat exchangers at the rear (in case of P168 - P234 models), 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 accumulator. 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) (only for P126-P234 models)
About this 4-way valve
When not powered:
The electricity runs between the oil separator exit and the heat exchanger (in the case of P126 - P144 model) HEXF,
between heat exchangers at the front(in the case of P168-P234 models), 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.
(3) In case of SV1 (Bypass valve)
This solenoid valve opens when powered (Relay ON).
1) At compressor start-up, the SV1 turns on for 4 minutes, and the operation can be checked by the self-diagnosis
LED display and the closing sound.
2) To check whether the valve is open or closed, check the change of the SV1 downstream piping temperature while
the valve is being powered.Even when the valve is closed, high-temperature refrigerant flows inside the capillary
next to the valve.
(Therefore, temperature of the downstream piping will not be low with the valve closed.)
Display
LD1 LD2 LD3 LD4
21S4a 21S4b
CH11
SV2 SV4a
SV1 SV3
*1 *1
SV5a
SV5b
*1
- 319 -
[ IX Troubleshooting ]
LD5 LD6 LD7 LD8
CH12
SV4b SV4c
*1 *1
SV4d
52F
*1
*1 Applicable to the PURY sereis only