Hitachi RAS-50YH4 Service Manual page 92

2. Outdoor unit does not operate (but receives remote infrared signal)
Set to room temperature 16°C in the cooling
mode or to 32°C in the heating mode, and
press the start/stop button.
Remove the outdoor unit cover and
electrical parts cover, and check self-
diagnosis lamp LD301.
Does LD301 blink one time?
*Repeats 0.25-second on and 2-second off.
Does outdoor electrical part
LD301 blink nine times?
Does LD303 switch off
several second after it lights?
Yes
Self diagnosis lamps
(LD303, 302, 301)
No
Yes
Is the indoor/outdoor unit
communication signal superimposed
on 35V DC of connection wires C
and D?
Approx.
35V
0V
Is the indoor transmitting signal
being generated at Q801's
collector?
No
Approx.
35V
0V
Yes
Perform final operation check.
38kHz Approx. 2Vp-p
Yes
38kHz Approx. 2Vp-p
Transmission waveform
Yes
– 102 –
Check the room temperature
thermistor; if it is defective,
replace it.
<Normal values>
10°C ➞ approx. 20kΩ
25°C ➞ approx. 10kΩ
30°C ➞ approx. 8kΩ
Check the heat exchanger
thermistor; if it is defective,
replace it.
<Normal values>
10°C ➞ approx. 20kΩ
25°C ➞ approx. 10kΩ
30°C ➞ approx. 8kΩ
No
Check outdoor electrical parts,
and repair any defective parts
(around the outdoor interface
transmitting circuit).
No
Check the indoor interface
transmitting circuit. Replace
IC801.
Check outdoor electrical parts,
and repair any defective parts
(around the outdoor interface
transmitting circuit).
Check outdoor electrical parts,
and repair any defective parts.