Carrier 38QUS012D8S Service Manual page 115

2.4.1.5. Indoor Fan Speed Malfunction
Malfunction conditions
Possible causes
Power off, then restart the
Power off, then restart the
unit 2 minutes later. Is it still
unit 2 minutes later. Is it still
displaying the error code?
displaying the error code?
Yes
Shut off the power supply,
Shut off the power supply,
rotate the fan by hand. Does
rotate the fan by hand. Does
it rotate properly?
it rotate properly?
Yes
Check the wiring of the fan
Check the wiring of the fan
motor. Are all the
motor. Are all the
connections in working
connections in working
order?
order?
Yes
Is the main PCB normally
Is the main PCB normally
operating according to index
operating according to index
1?
1?
Yes
Replace the fan motor. Is the
Replace the fan motor. Is the
problem resolved?
problem resolved?
Index 1:
1. Indoor DC fan motor (control chip is located inside the fan motor)
Power on and when the unit is on standby, measure the voltage of pin1-pin3, pin4-pin3 in the fan motor
connector. If the value of the voltage is not within the range shown in the following table, the PCB may be
experiencing problems and may need to be replaced.
DC motor voltage input and output
Electrical Control System
When indoor fan speed continues to run at too low a speed (300RPM) for a
certain period of time, the unit will stop and the LED will display a failure
code.
● Wiring mistakes
● Faulty fan assembly
● Faulty fan motor
● Faulty PCB
No The unit is operating normally
The unit is operating normally
Find the cause of the
Find the cause of the
problem and resolve it.
problem and resolve it.
For example,
For example,
No
be blocked or the screws
be blocked or the screws
which fix the fan in place
which fix the fan in place
No Correct the connections
Correct the connections
No Replace the main PCB
Replace the main PCB
No
the fan may
the fan may
are too tight
are too tight
Troubleshooting
113