AU-X095 - Sharp Air Conditioner Service Manual (repair manual). Page 19

19

The rotary four-way valve operates when a DC voltage is applied. When the current flows in the (a) direction shown in
the diagram above, the air conditioner is a heater, when the current flows in the (b) direction, it is a cooler. Power flows
in the rotary four-way valve for 1.5 seconds, and only flows just before the compressor is activated.

When activating the cooling operation, CPU IC1 pin 25 is LOW output and Q4 is OFF, so RY3 is on the D7 side. In this
state, if CPU IC1 pin 26 is set to HIGH output, Q3 goes ON, RY2 goes ON, and a half-wave rectification current flows in
the (b) direction, operating the four-way valve in the cooling mode.

When activating the heating operation, CPU IC1 pin 25 is set to HIGH output, Q4 goes ON and RY3 goes to the D8
side. By setting CPU IC1 pin 26 to HIGH output, Q3 and RY2 go ON. In this way, when RY2 is set to ON, the half-wave
rectification current flows in the (a) direction, and the four-way valve operates in the heating mode.

Both Q3 and Q4 are digital transistors and, like the outdoor fan drive circuit, are used to drive the relay.

CNR2 is connected to absorb the relay contact noise.

CPU (IC1) pin 26

CPU (IC1) pin 25

Noise

filter

circuit

Q4

13V

CNR2

CN4

N

1

Terminal
Block

Q3

D5

RY2

RY3

D10

D7

D8

Four-way
valve coil

a

b