8-4. Trouble Diagnosis of Fan Motor
8-4-1. Indoor Fan Motor
This indoor DC fan motor contains an internal control PCB. Therefore, it is not possible to measure the coil
resistance, and the following procedure should be used to check the motor.
To perform diagnosis, operate the unit in cooling mode with indoor fan speed "High". Next, make sure that the
indoor unit receive the signals from the remote controller when the ON/OFF operation button is pressed.
[Trouble symptom 1] The fan does not stop when the unit stops. Indoor unit controller trouble.
[Trouble symptom 2] The fan motor does not rotate when the unit is operating.
(Diagnostic procedure)
* Disconnect the motor connectors and measure the voltage at the DC motor connectors on the indoor
unit controller (3 locations).
(Diagnostic results)
All of the above measured values are normal. Fan motor trouble (Replace the motor.)
Any one of the above measured values is not normal. Indoor unit controller trouble
(Replace the controller .)
(Reference) DC motor connector pin arrangement
Pin 1: Vm (red)
Pin 2: Not used
Pin 3: Gnd (black)
Pin 4: Vcc (white)
Pin 5: Vs (yellow)
Pin 6: PG (blue)
[Trouble symptom 3] Motor rotates for some time (several seconds), but then quickly stops, when the indoor
unit operates.
(There is trouble in the system that provides feedback of motor rotation speed from the
motor to the indoor unit controller.)
[Trouble symptom 4] Fan motor rotation speed does not change during indoor unit operation.
[Trouble symptom 5] Fan motor rotation speed varies excessively during indoor unit operation.
(Remedy for symptom 3 to 5)
It is not possible to identify whether the trouble is indoor unit controller trouble or motor trouble.
Therefore, first replace the indoor unit controller, then (if necessary) replace the DC motor.
Important:
(A) Turn OFF the power before connecting or disconnecting the motor connectors.
(B) When performing voltage measurement at the indoor controller connector for (3) in the table
below, the DC motor will trip and voltage output will stop approximately 1 minute after operation
is started. For this reason, to measure the voltage again, turn OFF the unit once using the
remote controller, and then start the air conditioner again.
(1) Vm-Gnd: Between pin 1 and pin 3
(2) Vcc-Gnd: Between pin 4 and pin 3
(3) Vs-Gnd: Between pin 5 and pin 3
Measurement location
DC 230V or more
DC 14V or more
Fluctuation between DC 1.7 to 6.1V
Normal value
