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Solenoid Valve (SV1, SV2)
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.
SW1
LED
12345678
12345678910
ON
12345678910
ON
Compressor
operating.
Crankcase
Heater
Lights up
all the
time.
21S4 SV1 SV2
1) In the case of SV1 (Bypass Valve)
(a) When the compressor starts, SV1 is ON for 4 minutes, so check operation by whether the solenoid valve is emitting
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.
2) In the case of SV2 (Bypass)
(a) SV2 goes ON in accordance with the rise in the high pressure in the cooling mode and heating mode, so check its
operation by the LED display and the operating noise emitted by the solenoid valve.
(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.
✻
Connector connection specifications on the pressure sensor body side.
The connector’s pin numbers on the pressure sensor body side differ from the pin numbers on the main circuit board side.
Sensor Body Side MAIN Board Side
Vcc Pin 1 Pin 3
Vout Pin 2 Pin 2
GND Pin 3 Pin 1
CH 2, 3
Fluid
Level
Heater
-
45
-