Hitachi RAC-70YH7 Service Manual page 59

3. Reversing valve control circuit
Reversing
valve
V
DC voltmeter
or tester
Reversing valve control circuit can switch reversing valve ON/OFF according to instruction from indoor
G
microcomputer depending on the operation condition shows in Table 3-1.
Voltage at each point in each operation condition is approximately as shown below when measured by
tester. (When collector voltage of Q401 is measured)
Table 3-1
Cooling
Heating
Dehumidifying
CN2
4
D401
1
Q401
I/F 0V
Operation condition
General operation of Cooling
In normal heating operation
MAX. rotation speed instructed
by indoor microcomputer after
defrost is completed
Defrosting
Sensor dry
I/F 35V
12V
R437
1
4
PQ701
3 2
R435
R436
Fig. 3 – 1
Collector voltage of Q401
– 69 –
HIC
28
36
About 0.8V
About 35V
About 35V
About 0.8V
About 0.8V