Hitachi RAC-70YH7 Service Manual page 54

6. Room Temperature Thermistor Circuit
Fig. 6-1 shows the room temperature
G
thermistor circuit.
5V
Room
temperature
thermistor
R309
R310
A
0V
7. Heat exchanger temperature thermistor circuit
The circuit detects the indoor heat
G
exchanger temperature and controls
the following.
(1) Low-temperature defrosting during
cooling and
operation.
The voltage at A depends on the heat
exchanger temperature as shown in
Fig. 7-2.
Micro
computer
Room
64
temp. input
C302
0V
Fig. 6-1
5V
Heat exchanger
temperature thermistor
R307
R308
A
0V
Fig. 7-1
dehumidifying
The voltage at A depends on the room
G
temperature as shown in Fig. 6-2.
5
4
3
2
1
0
0
Micro computer
Heat
63
exchanger
C301
temperature
input
0V
5
4
3
2
1
0
-10 0
– 64 –
10 20 30
Fig. 6-2
10 20 30
Fig. 7-2
40
40