Intermittent PAS problem on BBS01B

Propellorhead

Just Joined
Jan 20, 2021
4
2
The bike has worked OK for a few months, but get intermittent power failure on PAS. Don't think it is battery connection or leads, because works with thumb throttle control. Have bought a PAS circuit board, but have not seen any diagrams or YouTube videos on where this is within hub & how far to dismantle. Is it part of the BBS01B controller?
 

Fordulike

Esteemed Pedelecer
Feb 26, 2010
3,674
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Tyne and Wear
Before you start replacing components, try one thing, if you haven't already. Finding a video on how to remove the final drive cog assembly will help here, but it's quite easy to do.

Remove crank arms and pedals, remove chainring, remove the plastic gear cover and unscrew the axle locking nuts (long needle nose pliers work here!)

Pull out the gear assembly, making sure you don't lose the thrust bearings on either end.

Clean the PAS sensor on the motor body (grease from the final drive can get trapped here)
Clean the area of the PAS disc (big plastic disc on back of large cog)

Put back together, making sure you tighten the axle locking nuts just enough to stop any free play. Too tight and you risk crushing the thrust bearings (whoops, wonder who did that recently :oops:)
 

Propellorhead

Just Joined
Jan 20, 2021
4
2
TQVM for that, I bought a special tool because I have 3 BBS01Bs so I will get some use out of it.
I was unsure how to remove the seal without damaging it.
(37 sec in) was clearest, used a small flatblade screwdriver without damaging seal.
Found the PAS circuit board and PAS disc. No scoring or visible dirt, but cleaned with isopropyl alcohol on qtip.
The PAS circuit board had some smears of white silicone straying 3mm onto board, so removed this.
Re-assembled, and sadly problem was still there, but now I know how to get at PAS.
Plan: Replace PAS board (have spare) (can I remove silicone and access connector via final drive - or do I have to remove controller?).
If that fails to work, replace controller (on order), and if no joy, replace whole motor.
Not fixed yet, but at least I didn't make it worse, and picked up useful skills on the way.
 

Fordulike

Esteemed Pedelecer
Feb 26, 2010
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There might be one more thing you can try, before replacing the PAS sensor. Haven't replaced PAS sensor myself, but doesn't sound like a fun job :oops:

Find a video on how to open up the controller side to expose the wiring inside. Check that all the connectors are correctly seated, as the silicon sealant they slap on during manufacturing, can cause the connectors to unseat over time.

I can't remember if any of the connectors actually connect to the PAS itself, so hopefully someone can come along and confirm if one of them does.
 

Propellorhead

Just Joined
Jan 20, 2021
4
2
I have reseated all the connectors in the controller.Made no difference. Replaced the PAS board. No difference (top tip - it comes with a black connector shell separate from the connectors. Don't insert connectors until wires are threaded through the hole in motor casing - it won't fit fully assembled).
Replaced controller - same intermittent behaviour.
I am now out of ideas. Once I replace the stator, rotor and disc magnet, that's all the electrics replaced!
 
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Pedaluma

Pedelecer
Sep 28, 2020
30
6
I have reseated all the connectors in the controller.Made no difference. Replaced the PAS board. No difference (top tip - it comes with a black connector shell separate from the connectors. Don't insert connectors until wires are threaded through the hole in motor casing - it won't fit fully assembled).
Replaced controller - same intermittent behaviour.
I am now out of ideas. Once I replace the stator, rotor and disc magnet, that's all the electrics replaced!
What is the gap between the magnets and pick-up? Is that properly aligned? I have found that to be the first and most simple cause to check. One guy installed the disc backwards another had some magnets with reversed polarity.
 

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Fordulike

Esteemed Pedelecer
Feb 26, 2010
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Tyne and Wear
What is the gap between the magnets and pick-up? Is that properly aligned? I have found that to be the first and most simple cause to check. One guy installed the disc backwards another had some magnets with reversed polarity.
The BBS01B is a mid drive motor with an internal PAS magnet disc and sensor. It's impossible to install the disc the wrong way round and usually only a cracked disc or faulty sensor causes problems.
 
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Pedaluma

Pedelecer
Sep 28, 2020
30
6
The BBS01B is a mid drive motor with an internal PAS magnet disc and sensor. It's impossible to install the disc the wrong way round and usually only a cracked disc or faulty sensor causes problems.
You are correct. I made a wrong assumption seeing that it was not the SO2.
 

Propellorhead

Just Joined
Jan 20, 2021
4
2
Problem "solved" - bought a BBS01B bare motor (no accessories) from greenbikekit. Costs about 60% of complete motor. Bike now works under PAS perfectly now. 2 other bikes with BBS01 in family, so now I have a load of spares! Will have a look at rotor / stator later to see if any scorching or debris. I suspect problem may have started when I was towing a trailer, and I overloaded motor, but post-mortem of motor will tell. Thanks for your ideas all, I was stuck!
 
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