Hitachi RAC-35NX2, Service Manual

Page: 125 / 194

6
5
4
3
2
1
1 8
15
10
2
7
4 5
6
3
14
11
12 13
IC6 C401
+
B-12V B-12V
R403 R404
PQ401
PQ402
PQ403
PQ404
CN4B
CN4A
R296
R295
R294
R293
1
2
4
3
8
9
11
10
39
40
41
42
5V
B-0V
R401
B-12V
CN15
Electric
expansion
valve
POWER P.W.B.
MAIN P.W.B.
Microcomputer
Valve4
Valve3
Valve2
Valve1
2 1 3 4
ON
OFF
OFF
OFF
ON
OFF OFF OFF OFF
OFF OFF
ON
OFF OFF
OFF OFF
ON
OFF OFF OFF ON
ON ON ON OFF
ON ON ON
ON
OFF OFF
OFF
Operation mode
1
→
2
→
3
→
4
→
5
→
6
→
7
→
8 VALVE CLOSE
8 → 7 → 6 → 5 → 4 → 3 → 2 → 1 VALVE OPEN
5 6 7 8
Drive status
Lead
wire
Blue
Orange
Yellow
White
①
②
③
④
①
②
③
④
200ms.
75ms.
50ms.
Pin No.
0.9V
12V
CN15
Pin No.
• To drive the expansion valve, use the B-12 V output. Use a 4-phase coil and feed power to the
phases 1 and 2, then switch over the filed poles to control the opening of the valve.
• The reference between conducting phase switch over direction and the open/close direction are
shown in Table 9-1. When the power is turned on, approx. 0.9 V is applied to the CN15 and the pins
( 1 to 4 ) and when no power is supplied, 12 V is applied. When the power is reset, the expansion
valve starts initial operation for 5 to 10 seconds.
• During the initial operation, measure each pin of the CN15 ( 1 to 4 ) with a multimeter. If no change
is found around 0.9 V or 12V in this step, the expansion valve or the micro computer has failure.
• The logic waveform during the operating of the expansion valve is shown in Fig. 9-2.
9. Electric expansion valve control circuit
Fig. 9-1
Fig. 9-2
Table 9-1
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