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5. Electric expansion valve circuit
Main P.W.B.
Electric
expansion
valve
Electric expansion valve is driven by B-12V. Opening of the valve is controlled by feeding power to 1
or 2 phases of the 4-phase coil to switch the polarity of the coil.
The relation between the conducting phase switching direction and open/close direction is as shown
below. When the power is turned on, approx. 0.9 V is applied to CN15 pins 1 to 4 ; when no power
is supplied, approx. 12 V is applied. When the power is reset, expansion valve performs initial
operation for 5 to 10 seconds.During initial operation, measure pins 1 to 4 of CN15 using
multimeter: If no change is found around 0.9 V or 12V, expansion valve or microcomputer is
defective.
Fig. 6-15 shows logic waveform during the operation of expansion valve.
CN 15
Lead
Pin No.
wire
1
2
ON
ON
White
Yellow
OFF
ON
OFF
O F F
Orange
OFF
O F F
Blue
1
2
3
4
5
6
8
7
6
5
4
3
50 ms .
Fig. 5-1
Table 5-1
Drive status
3
4
5
OFF
OF F
OF F
OFF
ON
ON
OF F
OFF
O FF
ON
O N
ON
O FF
OF F
OFF
ON
7
8
VALVE C LOSE
2
1
VA LVE OP EN
75m s .
2 00m s .
Fig. 5-2
– 95 –
H C
1 6
1 5
1 4
1 3
6
7
8
OF F
ON
OFF
OF F
OFF
OF F
ON
O N
12V
0.9 V
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