Mitsubishi Electric PUHY-HP200 Service Handbook page 198

[ IX Troubleshooting ]
-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. LEDs light up when relays are on.
The circuits on some parts are closed when the relays are ON. Refer to the following instructions.
SW1
SW1
1 2 3 4 5 6 7 8 9 10
ON
SW1
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:
Conducts electricity between the oil separator outlet and heat exchanger AND the gas ball valve (BV1) and the accumulator
to complete the circuit for the cooling cycle.
When powered:
The electricity runs between the oil separator and the gas ball valve, and between the heat exchanger and the accumulator.
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) 21S4b (4-way valve)
About this 4-way valve
while not powered:
Conducts electricity between the oil separator outlet and heat exchanger 1 (the top heat exchanger) and opens/closes the
heat exchanger circuit for the heating and cooling cycles.
when powered:
Conducts electricity between heat exchanger and the accumulator and opens/closes the heat exchanger circuit for the heating
and cooling cycles.
Proper operation can be checked on the LED and by listening for the operation sound. During heating, this valve turns on and
off simultaneously with 21S4a, sometimes making it difficult to listen for its operation sound.
In such cases, check the intake and discharge temperature for the 4-way valve to check the electricity runs between where
and where.
The 4-way valve becomes hot. Do not touch the valve to check its temperature.
Do not give an impact from outside, as the outer hull will be deformed leading to the malfunction of the inner valve.
HWE08110
LD1 LD2
Upper 21S4a
Lower
Upper
Lower
- 189 -
Display
LD3 LD4 LD5
CH11 SV1a
21S4b SV5b
LD6 LD7 LD8
SV2
SV6
SV9
GB