Three motors have stopped working. What could the cause be?

[DanJustDan]

Hey everyone, beginner here.

I've been following Oscar Liang's guide for building your first FPV racing drone and three of my motors have stopped working. I have the same parts Liang uses in the tutorial and after installing and testing in BetaFlight all motors, each motor worked just fine. I then installed the radio transmitter, tried to connect it with my Taranis qX7, and went to test the motors one last time. When I did so only one motor was spinning. The rest remained motionless whenever I throttled up in BetaFlight. Does anyone know where this problem could have originated?

Thanks

 

[DanJustDan]

Addition:

I've tried re-soldering my connections for one of the non-moving motors, but to no effect.

I've also swapped the signal wire and later the motors to test whether the motors or the ESCs are broken. Since the motor that spins is only on one arm, I know that the three motors are the cause of the problem, not the ESCs. Perhaps the dented packaging of the motors was a foreshadow to this predicament.

Edit: I replaced the motor on the spinning arm and found that the same arm worked perfectly. This likely means the ESCs are the problem not the motors, my mistake.

 

[tevek]

Addition:

I've tried re-soldering my connections for one of the non-moving motors, but to no effect.

I've also swapped the signal wire and later the motors to test whether the motors or the ESCs are broken. Since the motor that spins is only on one arm, I know that the three motors are the cause of the problem, not the ESCs. Perhaps the dented packaging of the motors was a foreshadow to this predicament.

Sounds a bit weird. If the motors spool up in Betaflight, I’m thinking the motors and esc’s are fine. If the Bell housings were dented, you wouldn’t be able to spin them by hand.
You say you have fitted the quad receiver and definitely bound it to your transmitter, set up the arm, mode switches etc in Betaflight. When you are in the modes tab of Betaflight, are you seeing the various switches working on the screen? If not, there is a possibility that your Tx and Rx are not bound but as to why only one motor would be spinning doesn’t make sense.
I guess you’ve already checked all your solder joints, particularly the incoming XT30/60 battery lead.

 

[HighTechPauper]

I can think of nothing that could cause what your describing short of breaking motor wires. Motors are pretty sturdy and simple. Unless you ran them at full throttle without props which is hard on them. Perhaps try to ohm out the motor wires to look for an open?

 

[DanJustDan]

Sounds a bit weird. If the motors spool up in Betaflight, I’m thinking the motors and esc’s are fine. If the Bell housings were dented, you wouldn’t be able to spin them by hand.
You say you have fitted the quad receiver and definitely bound it to your transmitter, set up the arm, mode switches etc in Betaflight. When you are in the modes tab of Betaflight, are you seeing the various switches working on the screen? If not, there is a possibility that your Tx and Rx are not bound but as to why only one motor would be spinning doesn’t make sense.
I guess you’ve already checked all your solder joints, particularly the incoming XT30/60 battery lead.

Sorry, I should have clarified earlier. I tried bounding my RC, but was unsuccessful. I then tested the motors and found that only one out of four spin when throttled in Betaflight. I replaced the motor on the working arm and found that it still spun without problems meaning the ESCs are likely the problem.

 

[DanJustDan]

I can think of nothing that could cause what your describing short of breaking motor wires. Motors are pretty sturdy and simple. Unless you ran them at full throttle without props which is hard on them. Perhaps try to ohm out the motor wires to look for an open?

When you say ohm out the motors do you mean probing each pair of wires to see if there's a short?

 

[HighTechPauper]

When you say ohm out the motors do you mean probing each pair of wires to see if there's a short?

Yes, but motors look like a short, usually around 3 ohms wire to wire. You want to check to make sure there is no open and that you get a low ohm reading.