Hub motor suddenly spins the wrong way, works after swapping phase wires but noisy and rough – what’s going on?

Posted by Kianushk@reddit | ebikes | View on Reddit | 29 comments

Hey Guys, So long Story short. I’ve got a 36V 500W geared front hub motor with a freewheel clutch. It used to work perfectly until yesterday. This morning, using the same wiring, it suddenly spun the wrong way: the motor rotated internally but the wheel didn’t move because the clutch didn’t engage.

I experimented by swapping two phase wires, and now it turns the correct direction again and the clutch engages but it’s loud, starts roughly, and feels kind of heavy.

I opened it up (photo attached): mechanically it looks fine. No broken gears, clutch is intact.

The 6-pin Hall sensor board seems okay on basic multimeter testing (reacts 0 V/5 V with a magnet).

Phase and Hall wires seem clean and well connected.

Controller shows no visible damage or smell.

My guess: maybe the controller mapping got scrambled or a Hall sensor is intermittently failing and feeding bad signals.

Has anyone seen this before? How would you debug next? Swap controller? Replace Hall board? Dou you see any damaged on the Picture?

Any tips or ideas appreciated! Thanks!

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Bubbly-Pirate-3311@reddit

Hello, as a person who can tell you a bit about brushless motors, you need to swap around some wires on the hall sensor board or it won't work right. Swapping phase wires without swapping the hall sensor wires confuses the controller and can lead to the controller burning out. My suggestion is that you put the phase wires back to how they were, and put the motor in the other way around so it's spinning the correct direction. If you want to fuck with the hall sensors (I don't recommend it) Google how to.

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Kianushk@reddit (OP)

That is unfortunally not possible, because like I said the Motor has a clutch and the clutch only drive in one direction. When is spun backwards I could hear it intern but the wheel wasnt moving.

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Bubbly-Pirate-3311@reddit

Ah that's right I forgot about the one way clutches. Yeah your hall sensor board is fried, so you'll need a new motor and controller

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Kianushk@reddit (OP)

I checked the Hall Sensor Board on the picture and I seemed all fine. How can I validate that it's the Controller?

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Bubbly-Pirate-3311@reddit

I dunno lol

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Ohm_Slaw_@reddit

Can you elaborate? You've got me curious. Do the motor and the halls need to sync up with each other? If the motor is firing red-green-yellow do the halls need to be firing red-green-yellow as well? If that is what's required then swapping the phases could be the cause of the motor running poorly.

I've heard of swapping phase wires to reverse direction, but it didn't mention messing with the hall sensors too.

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Bubbly-Pirate-3311@reddit

Yes they do! So the way Hall Effect Sensors work is by checking rotor position and phase, but if the phase order (IE red green yellow like you said) is different from what the hall sensors are programmed to think, it gets the motor in a weird state where the controller is trying to do one thing, but the sensors are screaming at it that it's doing the wrong thing, like a back seat driver. All this confusion gets the controller really confused, and it sometimes ends up frying the speed controller because it just cannot cope. The controller will be firing red green yellow, and the hall sensors need to sense what they're calibrated for, or they'll start doing what I said. When it's all nicely calibrated, it gives nice, smooth power at all points of throttle, but when it isn't nicely calibrated, you get the issues OP is having

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Ohm_Slaw_@reddit

That makes sense. I learned something, thanks!

Now the mystery that remains, is - why did op's motor mysteriously reverse itself?

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Bubbly-Pirate-3311@reddit

I never thought it would happen.... someone on the internet finally understood my incoherent explanation of something. Thanks!

I bet the controller just got a little messed up because of cheap build quality and is now misinterpreting signals from the throttle. It's weird though because I've never seen it happen before

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MrCrankset@reddit

FWIW I've seen controllers get confused like this dozens and dozens of times; one minute they work fine, the next they spin backwards. I don't know exactly why it happens but I've had to accept that it does!

It's always on controllers being used by delivery couriers so I assume it is a factor of heat and the strain related to that.

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Kianushk@reddit (OP)

Yeah that makes sense. Could be the Heat that build up, because most if the time the Controller are In a closed bag on the bike. But I didnt thought that they would be so fragile. Can i see or check if the controller is toasted if I open it?

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Kianushk@reddit (OP)

So you mean it's the Controllers fault? So the Motor is perfectly intact and whe I switch to a new Controller it should all work again? Maybe the Controller got to Hot and Fried itself somehow.

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Ohm_Slaw_@reddit

I think we're leaning towards a controller fault, yes. If you replace the controller, match it as close as possible to the original so it will work with the display. Also buy from someone who will sell you a display if you need it. Controllers and displays don't always work together, they are not universal.

The controller is much more complex electronically than the motor. Heat will kill it. There are far more points of failure.

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Kianushk@reddit (OP)

How can I check and find what the Problem is? I checked the Motor and the Hall Sensors with a Multimeter and it seemed all ok. And how do I check the Controller? Do I have to open it and Look for damage? If anybody had the same Problem I would appreciate the help Thanks

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hughdint1@reddit

Could you have put it on backwards? By switching the wires you may have it going the right way but maybe it is meant to go the other way and you need to flip it around.

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Kianushk@reddit (OP)

Thanks for your Reply but jo I used it for almost 100km like that, than suddenly it turned the other way. I think maybe it's the Sensors fault, because now the Start of the Motor is quite louder.

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MrCrankset@reddit

Check out this chart because you could experiment with changing hall sensor wires around before buying new kit

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Kianushk@reddit (OP)

Hello, Thank you that's interesting. Can you elaborate on that? How can I do it? Thanks

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Bubbly-Pirate-3311@reddit

The sensors may have failed, but swapping the phase wires without changing around the Hall sensor wires will confuse the controller even more and you run the risk of burning it out. I'd recommend buying a new motor and controller if you're not willing to mess around with a bunch of PITA wires

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DIYuntilDawn@reddit

Does your controller have a "self learning line" usually 2 white wires with a male and female connector, but would NOT usually be plugged together?

If so, first turn it on, then connect the wires. If it spins backwards, disconnect then, wait a second, then re-connect them again and it will spin slowly in the correct direction. Let it spin for about 10 seconds, then disconnect them and don't let them reconnect (or connect to chassis ground) by putting electrical tape over both of the ends.

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Kianushk@reddit (OP)

Hey, I dont thnik so it was a controller from a kit it think they are cheap one that dont have it. Is there another way?

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DIYuntilDawn@reddit

Then it is possibly something that was set at the factory where the kit was made, if the controller had a power spike or memory failure, it may have reset to a default state.

If you had to swap 2 motor phase wires to change the direction or rotation, then also make sure to swap the same 2 colored Hall sensor wires as well.

If you did swap 2 of both the phase wires and the hall sensor wires so that are all in reverse order now, and it is still making odd cluncky sounds and movement, then the controller has also probably lost other motor setting that need to be reconfigured. And if it doesn't have a self learning line, then those are usually set through either the display (if it has one that can do that) or via a programing cable and app (I know Bafang motors and controllers usually work that way) to set it up.

It could also be a faulty Hall sensor in the motor, you can get one of those brushless motor testers for like $20 on Amazon and a bag of like 40 Hall sensor is like $10 as well. Just be sure to get the same kind it currently uses.

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Mysterious_Bass6202@reddit

intermittend short in you 3 phase wiring.

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Kianushk@reddit (OP)

Can you See it on the picture?

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AcuMan_NYC@reddit

I was going to say something but then I noticed your motor has 4 hall sensors I have never seen that before so I don't know if changing the phase wires or the halls can help change the direction it spins. I would approach this via the controller settings. Not a thermistor!

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