Hitachi RAC-18SX8 Service Manual page 207

3. Failure phenomenon: The compressor will not run.
[ Situation ] The compressor will not run (the same state as the thermometer turned off), the product receives remote control
signals normally. The self-diagnosis lamp (LD301) of the outdoor unit blinks once or becomes turned off.
[ Estimated failure locations ] ・Room temperature thermistor, heat exchanger thermistor
[ Diagnosis flow ]
Initiating troubleshooting
Is the "timer lamp" (orange) or "monitoring lamp"
(yellow) of the indoor unit blinking?
Did the self-diagnosis lamp (LD301) of the outdoor
unit blink once or become turned off?
Remove the connector (CN4) of the room
temperature thermistor and heat exchanger
thermistor and measure the thermistor resistance.
Did the reading roughly agree with the resistance
values indicated in the right-hand figure?
Replace the "indoor electrical installation."
・Microcomputer peripheral circuit
No
Yes
Yes
Yes
Check for failures according to the self-
diagnosis display.
No
Check for failures according to the self-
diagnosis display.
No
Replace the "room temperature and heat
exchanger thermistors."
Thermistor characteristics (resistance)
40
30
20
10
0
0 10
Thermistor temperature
– 240 –
20 30 40 50
（℃）