The setup had been running perfectly for over 200km then suddenly one motor stopped working.
Applying any throttle causes the motor to jerk/jitter slightly, the red LED on the VESC blinks and a FAULT_CODE_ABS_OVER_CURRENT is logged (see included video). Motor detection also fails (see other video).
Using the arrow keys to spin the motor when connected to BLDC/VESC tool also causes stuttery movement.
I have tried these things without any luck:
- 3 different motors
- Rerunning motor detection
- Updating/changing firmware
- Checked motor phase wires + bullet connectors (visually and with a multimeter)
- Checked input capacitors (visually and with a multimeter)
- No signs of burn marks on the DRV chip
Is my VESC toast? 
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Look like one phase is down… probably one resistor or one mosfet. Could you post some closeup picture of the VESC?
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I think you’re onto something @JohnnyMeduse.
When unplugging one particular phase wire (I can’t remember which exactly) and hitting the throttle, FAULT_CODE_ABS_OVER_CURRENT wasn’t being thrown. Connecting the “suspect” wire back, along with any one of the other two resulted in the fault again.
I’ll upload some closeups when I’m home from work. Thanks!
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Just shout if you need any more photos to complete your detective work. The phase wire soldering looks a bit dodgy but that was because of me yesterday with a soldering iron.
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Humm… There nothing here that is visually striking. If you have a multi-meter I would recommend to check if one of the mosfet is shorted, and if R48 to R51 are 100Ohms.
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Welcome. I’m sure the smart gentry will get your VESC issue figured out, but in the meanwhile I have matched your trust level from Builder’s Forum.
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@JohnnyMeduse both R48 and R51 checkout at 101 ohm. Is it possible for me to test the mosfets using this method while they are still soldered onto the PCB? Or would I need to remove them for an accurate result?
Thanks @BillGordon. I didn’t realise there was a mass exodus from the-place-that-shall-not-be-named until a few weeks ago.
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Usually what I do is put the multimeter in diode check mode, put the positive lead on the gnd of the vesc and touch each phase with negative lead. Repeat the process with the mutimeter lead inverted the negative one on the Vin of the vesc, and the positive lead on each phase.
I have done some video with a focbox https://www.youtube.com/channel/UCo3fMYtsfrZR82vuqvJYEuw?view_as=subscriber
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Just watched all your videos @JohnnyMeduse, interesting stuff. It seems like the mosfets checkout OK using your method. They all read the same value when in diode mode: lower 400s. Are there any other components I can measure?
yes, you could check the mosfet resistor which are suppose to be 4.7Ohms and 39KOhms.
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Thanks for the schematic @JohnnyMeduse. I just measured all the mosfet resistors and found some strange values:
R28 = 16.6 ohm (should be 4.7 ohm)
R29 = 16.6 ohm (should be 4.7 ohm)
R30 = 39k ohm (correct)
R34 = 43.8 ohm (should be 4.7 ohm)
R35 = 44.2 ohm (should be 4.7 ohm)
R36 = 39k ohm (correct)
R42 = 32.5 ohm (should be 4.7 ohm)
R43 = 33 ohm (should be 4.7 ohm)
R46 = 39k ohm (correct)
So it looks like all the low value resistors (4.7 ohm) are now reading much higher values. Any idea what this could indicate?
That is weird, usually if they had a failure they would show a value around one 1MOhms, I could just be the Multimeter that as problem reading low value.
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You’re right @JohnnyMeduse. I borrowed a friend’s multimeter and the resistors all checked out perfect. Here are the updated readings:
R28 = 5 ohm
R29 = 4.9 ohm
R30 = 39.1k ohm
R34 = 4.8 ohm
R35 = 4.9 ohm
R36 = 38.9k ohm
R42 = 5 ohm
R43 = 4.8 ohm
R46 = 38.9k ohm
Do you have any more suggestions what components I could check/measure?
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