Electric Expansion Valve Circuit - Hitachi YUTAMPO Series Service Manual

4 Electrical checks of main parts
Outdoor unit

4.1.6 Electric expansion valve circuit

Electric
expansion
valve
RED
The electric expansion valve is driven by DC12V. Power is supplied to 1 or 2 phases of 4-phase winding to switch
magnetic pole of winding in order to control the opening degree.
Relationship between power switching direction of phase and open/close direction is shown below. When power is
supplied, voltages at pins 4 to 1 of CN15 are about 0.9V and 12V when no power is supplied.
When power is reset, initial operation is performed for 10 or 20 seconds. During initial operation, measure all voltages
at pin 4 to 1 of CN15 by using a multimeter. If there is any pin with voltage that has not changed from 0.9V or 12V,
expansion valve or micro computer is broken.
Figure below shows logic waveform when expansion valve is operating.
CN15 pin
number
Operation mode
Connector
pin number
With expansion valve control, opening degree is adjusted to stabilize target temperature by detecting compressor head
temperature. The period of control is about once per 20 seconds and output a few pulse.
41 SMGB0135 rev.0 - 06/2020
14
12
10 7
8
Wire
Valve close
Valve open
48
13 4
47 14
3
46 15
2
45 16
1
Drive status
Microcomputer
68
67
66
65
4