Hitachi RAD-18NH7A Service Manual page 86

3. Only indoor fan does not operate (other is normal)
Is approx 20 V DC generated
between pins (blue) and
2
CN 10 when operated at high fan
speed during cooling?
No
Are pulses of approx. 33 Vp-p
generated at the collectors of Q901
in the fan operation mode? Are
collectors of Q903 approx.
O V?
Yes
Are microcomputer fan PWM
outputs (micro computer pins
or are pulses output
in the fan operation mode?
No
4. Indoor fan speed does not change (other is normal)
Has the fan been stopped by
remote control?
No
Yes
Is 5 V DC generated between pins
(red) of
4
(blue) and
No
Is there 1 Ω or less between L901
and L902?
Yes
)"Hi"
24
Perform final operation check.
Yes
Are microcomputer fan PWM
outputs micro computer pins
Are the collectors of Q903 approx
OV?
Perform final operation check.
2
(yellow) of CN10?
1
No
No
Yes
"Hi"?
54
No
Yes
No
– 96 –
Yes
Replace indoor fan motor.
Check disconnection, etc of lead
wires.
Yes
Replace Q901.
Replace L901.
Replace Q903.
Replace micro computer.
Replace micro computer.
Replace Q903.
Replace Q901.
Replace micro computer.