Jittery motor problem

[Dune]

I'm flying a stock DJI f450 with Naza.

One of my motors (back right, motor #4) when armed just kind of twiddles its thumbs. Instead of spinning, it jerks back and forth, sometimes making a couple slow rotations in either direction.

What could this be?

It is an intermittent problem. Seems to happen randomly - was on and off last night. Today, I flew my first flight, landed for literally 5 seconds and tried to fly again, and the jitter surfaced again. I could not get it to work normally for 15 minutes and finally gave up. All I've done to troubleshoot is power cycle, wiggle wires and unplug/replug stuff back in.

Here are some possibilites.
Bad Connection:
Rx to Naza (This seems very unlikely)
Naza to ESC (This is my main suspect)
Power to ESC
----
Bad Motor
Bad ESC
----

I could take this thing to school and look at the ESC with an oscilloscope if need be.

Edit: Now, sitting at home it's doing it on/off again. Every other time it will work, and then it won't The behavior appears similar to if I unplug one of the motor plugs from the ESC. EXCEPT I just discovered if I give the prop a good push in the right direction, it will start up and work fine!!! Hah! Sometimes upon arming after a few seconds of jittering it will catch on and start spinning too. Perhaps this explains why I'm not crashing left and right.

 

[Elliott000]

I was told to check the fittings on the end of the motor for broken solder... Did that all was fine so i spoke to my dealer and got a new one in the mail

Sent from my GT-I9100M using Tapatalk

 

[Dune]

Are you talking about wire -> esc connection? Those joints look fine.

Took the motor apart, was interested to see the wires don't terminate inside, they just exit the wire casing and join the wire wound round the motor.

For now I'm going to use a spare motor I bought, and call up my supplier soon.

 

[mailman35]

the brushless motors work by just going to different sets of the coils, hence why you can plug them in how ever you want, and then just reverse the 2 of 3 cables.

 

[1Proto7]

Jitter problem

Your jitter is being caused by the wire connections between that motor and the ESC. I promise, no matter what you have already checked and believe to be ok. That' s it.