Hitachi RASC-4HNPE Service Manual page 288

10 Troubleshooting
Checking procedure for main parts
4-way solenoid
valve coil
4-way solenoid valve
Bistable solenoid operation type (pulse-activated)
Operation Mode: Cooling → Heating
Reversing Valve: OFF → ON
When current is applied to the reversing valve coil, an
electromagnetic force headed in the same direction as the
magnetic force is generated, and the valve is turned ON by their
attraction. After the valve is turned ON, the plunger position is
kept by magnetic force with no current applied.
Magnet
Magnetic
screw
Coil case
When the reversing valve is
turned ON (Current Applied)
After the reversing valve is
turned ON (No Current Applied)
278 SMGB0091 rev.2 - 11/2015
Electrical circuit
Time Chart
Heating operation
Coil voltage
Attractor
Coil Plunger
Spacer
Plunger position
Magnetic+Electromagnetic
force (Attraction)
Spring force (separation force)
Electromagnetic force
(Position-keeping force)
4-way solenoid
valve coil
Cooling operation
or
Defrost operation
Heating operation
Current is continuously
carried while the reversing
valve is ON.
is turned ON
Operation Mode: Cooling → Heating
Reversing Valve: OFF → ON
When current is applied to the reversing valve coil, an
electromagnetic force headed in the direction opposite to the
magnetic force is generated, and the valve is turned OFF by
their separation force. After the valve is turned OFF, the plunger
position is kept by spring force.
Magnet
Magnetic
screw
Coil case
When the reversing valve is
turned ON (Current Applied)
After the reversing valve is
turned ON (No Current Applied)
Coil Attractor
Plunger
Spacer
Plunger position
Magnetic force (Attraction)
Spring+Electromagnetic force
(separation force)
Spring force (Position-keeping force)