Mitsubishi Electric PUHY-P200 Service Handbook page 138

3. Solenoid valve
Check if the control board's output signals and the operation of the solenoid valves 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. When a LED lights up, it indicates that
the relay is ON.
✻The circuit is closed when the relay is ON depending on parts. Refer to the following instructions.
SW1
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 whatever valves malfunction, check whether the solenoid valve coil is not attached wrongly, 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 the case of SV1 (Bypass valve)
This solenoid valve opens when powered (Relay ON).
(a) When the compressor starts, SV1 is ON for 4 minutes, check operation by whether the solenoid valve is emit
ting an operating noise.
(b) Changes in the operating condition by solenoid valve operation can be confirmed by the temperature of the
bypass circuit and the sound of the refrigerant.
(c) SV1 goes on in accordance with the rise in high pressure in the cooling and heating mode, check operation
by LED display and the operating noise emitted by the solenoid valve.
(2) In the case of SV3 (Bypass valve) (Only P450-P650 types)
This solenoid valve opens when powered (Relay ON).
The valve is normally powered while No.2 Comp is being stopped.
(When the discharge temperature of No.1 Comp exceeds 110˚C, the valve may be turned off.)
To check whether the valve is open or closed, check the change of the SV3 downstream piping temperature
while the valve is being powered. When the valve is open, high-temperature gas will run. Do not touch the pipe
when checking the temperature.
(3) In the 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 the case of
When powered : The electricity runs between the oil separator and the gas ball valve, and between the heat
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.
1 2 3
21S4a 21S4b 21S4c
SV1 SV3
SV5b SV5c
P400 type) HEXB, between heat exchangers at the rear (in the case of P450-P650 types),
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.
exchanger and the accumulator. This circulation is for heating.
LED
4 5
CH11 CH12
- 136 -
6 7 8
52F