3DR Hexa APM 2.5 only 4 of 6 motors spinning

To start off, Hello everyone.  I am new to the community (although far from new to assembling/hacking electronics) and have purchased and assembled a 3DR Hexa with the uBlox GPS and 880 motors.  The main problem I am having (among others) at the moment is that only 4 of the 6 motors are spinning after arming them.  Motors 3-6 will spin just fine, they will arm and disarm and generally they will function normally.  Motors 1 and 2 will not spin, and I have no clue why. (yes I have ensured that I flashed the correct firmware to the board, yes I updated MP to version 1.2.20)

I am using a Spektrum DX8 with the AR8000 receiver.  I have manually calibrated each and every ESC, and none of them are beeping at me.  All solder connections on the power distribution board have been checked, and none are shorted, as well as all of the solder connections I made on the APM board itself. I have triple checked all non solder connections and ensured all the cables are going to their proper places and are not shorted to ground/power/each other.  I have ensured connectivity at each end of all the cables where possible.

Also, the Auto ESC Calibration will not initiate for some reason.  I have adjusted trim levels on the Tx to no avail.  I am fairly certain that this is part of the problem above, however I do not have a solution fo that either.  I have been browsing the forums for the past few days trying to figure this out.

If anyone has any suggestions I would greatly appreciate them.  I am trying to have this copter ready by Thanksgiving in order to film the testing of my friend's pumpkin trebuchet from the air.

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  • Austin,

    Have you turned on motor logging? I would check if the motors are receiving the output from the APM.

    I had a problem like this and found my frame was set to HEX instead of Quad. I noticed it when I checked the logs.


  • Moderator

    Hi Austin, What happens when you run the 'Motor' test through the CLI? Still only 4 from 6 motors spin?

  • Have you tried swapping around the wires from the APM to the ESCs? If #3 works and #1 does not, try swapping the connections to the APM. If the problem stays the same, you have a software or APM problem. If #1 works and #3 does not, then you have an ESC or motor problem.


  • Simplest possibility - are you set to hexa and not quad?  You can test the motors/ESCs individually by putting the ESC's UBEC cable straight into your receiver's throttle channel - I assume this is how you calibrated them, so they must work, but did you run the motors up at the same time?....  um...  I'm thinking it's a APM planner/code set-up thing.  

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