BMC Motor won't run and it is slowly driving me insane

[jc4291]

I have a BMC motor that appears to be having some hall sensor problems. Motor makes very sad grinding noises when power is applied, but turns freely forwards and backwards with no power.

I had probed the blue, yellow, and green wires while turning the motor backwards to see the voltage change and found 1 sensor that was constantly reading 4.8 volts.

I thought, ok, no problem, replace the sensor then be on my way. Replaced the sensor, and found the problem was still present.

I inspected the wiring harness to find that it was worn and possibly shorted, perhaps taking the sensor with it. So I replaced the entire wiring harness (phase and sensor wires) with brand new ones - taking a considerable amount of time. I replaced the sensor for good measure incase I had blown it by sending power to a phase wire shorted to the sensor.

Still, exact same problem as before. Motor makes very sad grinding noises and sensor constantly reads 4.8v no matter the position of the wheel. I replaced the sensor with a Honeywell SS41 and the wiring harness completely. Sensor shows conductivity to the correct pins, and other 2 sensors behave as they should. Double checked order of the wires I reconnected to rule out a miss-routed wire.

I have no idea what else to do. Any advice?

 

[amberwolf]

What does it do with a different controller?

Keep in mind that if a phase did short to a hall, it could've taken out the controller's hall input, too.

 

[dogman dan]

It does sound to me like it dies the instant you plug into that controller.

 

[wineboyrider]

Those motors are also real picky with sensorless controllers too. I have an old school crystalyte sensorless that runs mine with one messed up hall sensor. Oh and the hall sensors are a little bit trickier to repair than DD hubs. :?

 

[spinningmagnets]

If it turns freely forwards and backwards, maybe its the clutch? (inside the hub). Its been a long time since I had a geared hub, so maybe I'm not remembering correctly...

 

[jc4291]

What does it do with a different controller?

Keep in mind that if a phase did short to a hall, it could've taken out the controller's hall input, too.

This is a very real possibility actually, however I do not have another controller, is there a different way to test this?

 

[izeman]

Sure. There are instructions on how to test hall sensors and how to test FETs for shorts. You will need to search the forum. You will need a DMM though.

 

[teklektik]

Motor testing info here.
Ebike Tester info here.

 

[amberwolf]

Keep in mind that if a phase did short to a hall, it could've taken out the controller's hall input, too.

This is a very real possibility actually, however I do not have another controller, is there a different way to test this?

To test the halls on the motor without the controller connected, there are instructions on the wiki and on the grin tech site http://ebikes.ca , as well as around the forum.



To test the controller hall inputs for shorts,
--Disconnect the motor halls from the controller.
--measure each of the 3 hall input pins at the controller hall connector (not the motor); they should all read about 5V. If one doesn't, it is probably the problem.

--If they all read correctly, then if you have a bare resistor (5-10kohm should work), you can connect that from ground on the controller hall connector (not the motor) to each of the hall inputs in turn (on the controller hall connector, not the motor), while measuring the voltage with the multimeter.

Any input that doesnt' go to a low voltage means something is shorted inside the controller.

If none of them do, and all the hall inputs on the motor toggled ok, then it is probably something with the MCU itself. You can open it up and trace the hall input back to the MCU pin, and see if the non-responsive one has a place anwyhere in there that doesnt' match what the others do as you toggle them manually with the resistor to ground at the connector pin.