One motor not working right. Need Advice

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While flying the other day I bumped into a tree. It broke one of the prop guards but the prop itself seems fine. after fixing guard I went to fly it again and that one motor doesn't spin correctly. It's very jittery at idle speed and won't accelerate like the other three. I don't know if it's the motor or the main control. How do I troubleshoot this problem? Need some experienced help!
 
While flying the other day I bumped into a tree. It broke one of the prop guards but the prop itself seems fine. after fixing guard I went to fly it again and that one motor doesn't spin correctly. It's very jittery at idle speed and won't accelerate like the other three. I don't know if it's the motor or the main control. How do I troubleshoot this problem? Need some experienced help!


When you say fixing the guard, what do you mean?
It is a common mistake to put the screws used to hold the guard on back on the arm without the guard.
They are too long and at full insertion will intefere with the motor windings and ruin the motor.

Assuming you're good there...

Typically the motor is fine after a strike or stall.
However the ESC is prone to failure during a stall period.

Assuming there is no physical damage to the motor from a crash or screws then the ESC is the most likely.
Cause of your problem.
 
When you say fixing the guard, what do you mean?
It is a common mistake to put the screws used to hold the guard on back on the arm without the guard.
They are too long and at full insertion will intefere with the motor windings and ruin the motor.

Assuming you're good there...

Typically the motor is fine after a strike or stall.
However the ESC is prone to failure during a stall period.

Assuming there is no physical damage to the motor from a crash or screws then the ESC is the most likely.
Cause of your problem.
I used on epoxy to repair the broken guard before putting it back on........however, I did put the screws back in to holes so I wouldn't loose them. I didn't really tighten them down but I may have run them in far enough to do damage. ugh! Where would I get a motor and how bad a job is it to change one?
 
I can't recommend a vendor cause I haven't any experience with them.

But there are several vendors who sponsor our site by posting their adverts.

Give one a shout!!!

Change out requires soldering experience - three wires.
 
I can't recommend a vendor cause I haven't any experience with them.

But there are several vendors who sponsor our site by posting their adverts.

Give one a shout!!!

Change out requires soldering experience - three wires.
Thank you very much for your help. I really appreciate it.
 
IF! you are good at soldering it a cake job to replace a motor or esc.
 
IF! you are good at soldering it a cake job to replace a motor or esc.
Many, many years ago I used to fix circuit boards (back in the old days when you could repair them) so that shouldn't be a problem. I can't see any damage to the motor windings but it hard to tell even with a magnifier and bright light. I'm thinking it might be the ESC?? That doesn't look too bad to change either. Is there a difference in the ESC's other than the order in which the motor wires connect to it? I was think about swapping it with one of the others to see if it's bad.
 
The FC40 (P1) ESCs are sold as red or green, depending on the color of the LED. Really, they are both the same except for the location of one resistor.

You can test a motor by measuring the resistance across all 3 pairs of wires (red yellow, red black, black yellow). Should all be the same.
If one is double the other two, then you've got a broken coil. You should be able to do this test even when the motor is attached to an ESC,
assuming the ESC isn't broken. Note that DJI coats everything with clear gunk, so you need sharp probes to penetrate it.
 

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