Hitachi RAS-20CNHZ2 - Page 96

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RAM-50CNHZ2
1. Outdoor unit does not operate (remote control signal can be received)
In hot weather, set operation mode to cooling,
room temperature to 16°C; in cold weather, set
to heating mode and 32°C, and then press
operation button.
Remove outdoor unit cover and
electrical parts box lid, and check
LD301 self-diagnosis lamp.
Does LD301 blink once?
❈ Repeating to light for 0.25 sec.
and go off for 2 sec.
No
Does LD304 in electric parts
box blink once when only one
indoor unit is connected?
Does LD303 go off a few
seconds to ten and few seconds
after it is lit?
Perform final operation check.
Check electrical parts of outdoor
unit and repair defective parts.
Check electrical parts of outdoor
unit and repair defective parts.
(Around outdoor interface
transmitting circuit).
Check indoor interface
transmitting circuit.
Check electrical parts of outdoor
unit and repair defective parts.
(Around outdoor interface
transmitting circuit).
Check room temperature thermistor.
If defective, replace it.
[Normal values]
10°C ➞ approx. 20kΩ
25°C ➞ approx. 10kΩ
30°C ➞ approx. 8kΩ
Check heat exchanger thermistor.
If defective,replace it.
[Normal values]
10°C ➞ approx. 20kΩ
25°C ➞ approx. 10kΩ
30°C ➞ approx. 8kΩ
Is indoor/outdoor communication
signal superimposed on DC35V?
During check using tester:
If superimposed, 35V rapidly
changes.
Caution:
Digital tester only.
Is indoor transmission signal
generated at Q803 collector?
During check using tester:
If generated, voltage rapidly
changes between 4V and 0V.
No
No
No
Yes
Yes
Yes
Yes
0V
About
4V
38kHz
Transmission waveform
of about 2Vp-p
0V
About
35V
38kHz
Transmission waveform
of about 2Vp-p
Service Switch
LD301