Troubleshooting A/C fan motor

[soldar]

A friend asked for my help in troubleshooting a problem with the fan of the motor of the evaporator of a split A/C system. He is in another town so I do not have access to the system myself.

He says the motor will not start and the system detects no rotation and will stop and give an error code. He says if he helps it start then it will rotate and work OK. Mechanically the motor shaft rotates completely freely. No mechanical resistance.

He thought it might be the motor so he bought a replacement but the problem persists. Once the motor starts rotating it works fine so he pushes it a bit to help it start and later just keeps the AC running so he raises the setpoint so the compressor is not working but the fan keeps running. For now he gets by like that.

He sends me the attached photo of the motor which has a schematic of the connections.

It has two connectors with three cables each. The main connector has Red and Black wires which are the main for power supply and a white for the capacitor. I suggested the capacitor on the main board might be bad but here is where things beging to get strange because connecting the motor to the board produces the problem I described: it does not start. But if he connects 230 V directly from mains to red and black then the motor starts and runs fine. With no external capacitor.

Question the first: Is it possible the capacitor is inside the motor housing? Included with the motor? Seems like this would explain why the motor starts fine. But if the capacitor is included with the motor why the need for the white wire to go to the control board?

Also, I do not understand the purpose of the other three wires but I suspect they are a speed sensor reporting back to the control board.  But why that capacitor in the schematic? Anyone know more about this motor?

And how is the motor speed controlled? Just a resistor inserted in series? Because there is only one winding, no taps.

If I had access I would try to measure voltages, waveforms, etc. but, as I say, I am far away and cannot do this.

What do you think? Any suggestions or advice?

Edit: The three white wires on the right are the Feedback Generator and they are Gnd, Vcc and Output.  I think it is safe to assume that part is working OK.  My inclination is to suspect the motor is receiving insufficient voltage between Red and Black.

[indeterminate]

Replace the capacitor, it is there to start the motor.

Motors can start but unreliably with no cap & no load.

https://en.wikipedia.org/wiki/Induction_motor