Only The Indoor Unit Fan Does Not Operate; The Fan Speed Of The Indoor Unit Fan Cannot Be Changed - Hitachi RAS-25CNH1 Service Manual

4. Only the indoor unit fan does not operate (other functions are normal).
Is a voltage of DC25V-35V generated
between pins
(Blue) and
of CN10 when operated in the
"HIGH" fan speed mode?
NO
Is a pulse of about 33Vp-p generated
at the callector of Q904 in the fan op-
eration mode?
Is the voltage collector of Q904 ap-
prox. 0V at this time?
Is the fan PWM (Pulse Width Modula-
tion output (pin of micro computer
57
set to"Hi" or is the pulse waveform
output when operation mode?
NO
4. The fan speed of the indoor unit fan cannot be changed (other functions are normal)
The fan cannot be stopped by the re-
mote controller.
NO
YES
Is a voltage of DC 5V generated be-
tween pins
(Red)
of CN10?
NO
Is the resistance between L901 ter-
minals Ω or less?
YES
Perform a final check of operation.
YES
Is the fan PWM output (pin
micro computer set to "Hi?
Is the voltage collector of Q904 ap-
prox. 0V?
Perform a final check of operation.
YES
(Blue) and (Yellow)
NO
YES
NO
YES
of the
57
YES
NO
– 100 –
Replace the indoor unit fan motor
Check whether the P.W.B. pattern is
shorted and replace REG2.
Replace Q903
Replace L901
Replace Q904.
Replace the micro computer.
Replace the micro computer.
Replace Q904
Replace Q903
Replace the micro computer.