Fly 600/Magic Pie troubleshooting

[twm]

I've been having increasingly nasty problems with my Fly 600, culminating in its complete non-operation.  I believe I have a 36V pack (it reads ~41V with a multimeter when freshly charged), if it's relevant.  I have checked that the brake switches work (though they appear to be normally-open, which I find suprising).  The cruise control switch also works (normally-open).

Current Symptoms
On turning the key to the on position, the red and yellow battery indicator lights on the throttle illuminate.  This doesn't match the battery indicator on the battery pack, which reads full.  Twisting the throttle doesn't produce any movement.

Prior Symptoms
When the problem first presented I suddenly found that the brakes didn't cut the motor, nor did releasing the throttle or canceling cruise control.  Fortunately the disc brakes are able to halt the wheels, and cutting power (by turning the key) reset the system.  After this, I found that twisting the throttle causes the motor to begin accelerating, but nothing short of cutting power could get it to stop (it would continue accelerating up to full throttle regardless of how much the throttle was turned).  Even more strangely, it only exhibited this behavior under load --- if the wheel wasn't on the ground the throttle behaved normally.  The lights were still wrong, only the red and yellow LEDs illuminating.

Can anyone suggest a cause, or what I should do next to identify the problem?  I fear that the motor controller is broken, but I haven't yet worked up the courage to open up the Magic Pie, and I'm not really sure how to make that determination anyway.  I haven't been able to identify any issues with the wiring harness, though I haven't followed it all the way down into the Pie.

[Bikemad]

This non running problem could also be caused by a broken ground wire on the main harness. If the throttle is activated when the controller is turned on, there is a protection system which prevents the motor from running until the throttle has been released.
A broken ground connection on the throttle can cause a full throttle signal to be sent to the controller which would also activate this protection system.

I strongly recommend that you suspend the bike (or put it on blocks etc.) so the driven wheel is off the ground, because if you move the harness and momentary make and break a connection on a faulty ground circuit, it could instantly re-enable the throttle, which would then cause the motor to start running flat out!

Check out this post for a quick way of checking the motor and controller to determine whether the fault is on the motor/controller side, or on the harness/handlebar controls side.

If the fault is on the harness side, and you can access the connector for the throttle, check the voltage between the red and black throttle wires to see if you have ~5V:

• If the voltage reading is correct, check the voltage between the throttle signal wire (might be green or white) and the black throttle ground wire.
  This voltage reading should gradually change from ~0.8V to 4.5V as the throttle is slowly moved from low to high.
   
• If the voltage reading is not correct, check the voltage between the black throttle ground wire and the battery negative connection. if its more than 0.5V, there is definitely a problem with the ground connection, as it should ideally read 0V.

Please let us know what you find.

Alan
 
P.S. If the green LED on the battery meter has never lit up, it's possible that it may have had a 48V throttle control accidentally fitted (as they all look the same) instead of a 36V one.

[twm]

Check out this post for a quick way of checking the motor and controller to determine whether the fault is on the motor/controller side, or on the harness/handlebar controls side.

Shorting those pins made the motor spin all-out, so I guess it's on the throttle side.

If the fault is on the harness side, and you can access the connector for the throttle, check the voltage between the red and black throttle wires to see if you have ~5V:

I read a steady -0.740 V between the red and black, but the wire between the harness and the plug reads as intact.  I guess it's the throttle itself.  Any tips on troubleshooting it?  I'm having some trouble getting it apart.

Thanks a lot for your help!

[twm]

Well, I've gotten the throttle apart and am mystified to find that the wire reads as continuous.  So do the red and white ones.  Could something be wrong with the little chip it's attached to?

Edit: Actually, the test of the pins on the motor socket before didn't cover the ground wire there.  I get no connectivity between pin 2 coming from the motor and the ground pin on the battery connector.  Should there be?

[Bikemad]

Actually, the test of the pins on the motor socket before didn't cover the ground wire there.  I get no connectivity between pin 2 coming from the motor and the ground pin on the battery connector.  Should there be?

Yes, you should definitely have continuity between pin 2 and the battery ground connection as they are both connected via a common ground connection strip on the controller PCB.
It must be a break in the thin black wire, somewhere between the controller and the 8 pin round connector socket, and you should have been able to detect a faulty ground connection when you checked the voltage between the black throttle ground wire and the battery negative connection, as it would have been over 5V with a broken ground connection.

Anyway, now you've located the problem, the quickest and easiest way to rectify it is to run a separate wire from the battery negative connection to the black wire on the main harness. A thin wire is all that is really required to carry the small amount of current, but a thicker wire can always be used if that's all you can find.
 
The alternative is to replace the complete motor harness, but that would be a far more involved and complicated repair.

I hope you are able to carry out the repair without too much hassle and hopefully get your bike back in action again pretty soon.



Alan
 

[twm]

I ran a 22 ga wire from the battery connector (just jammed it in there) up to where all the negative wires meet, and that seems to have solved the problem.  The bike works again

Oh, and I think that I forgot to mention before that the headlight cable burned through its insulation a few weeks before it stopped working (there was a big white spark as I was riding the bike, but no other immediate symptoms).  Could this be the root cause?  Could the short have caused the ground wire to fail later?

Thank you very much for your help!