Hitachi RAS-18YH4 Service Manual page 60

8. Reversing valve control circuit
Reversing
valve
DC voltmeter
or multimeter
Reversing valve control circuit will switch reversing valve ON/OFF(cooling ON) according to instruction
from indoor microcomputer depending on the operation condition shows in Table 8-1.
Voltage at Q701 (between Collector and Emittor) in each operation condition is approximately as shown
in Table 8-1 when measured by multimeter.
Cooling
Heating
Dehumidifying
Power P.W.B.
CN2
2
D701
4
Q701
R705
V
D-0V
Fig. 8-1
Table 8-1
Operation condition
General operation of cooling
In normal heating operation
MAX. rotation speed instructed by indoor
microcomputer after defrost is completed
Defrosting
Sensor dry
C-35V
12V
R701
PQ701
CN4A
CN4B
6 6
R706
Collector voltage of Q701
– 63 –
MAIN P.W.B.
Microcomputer
24
About 0.8V
About 35V
About 35V
About 0.8V
About 0.8V