New build: pas sensor intermittent cut-out

[Chees]

Hi all,

I finally got around to putting together the KT+Bafang kit I got and almost everything seems to be working well. The only problem is an issue with the pas sensor.

The PAS is a 12 pole split ring disc (like this one: https://www.amazon.co.uk/TOOGOO-Electric-Bicycle-Conversion-Accessories/dp/B07VQ97P5T/), and the red light lights up when the each point passes the sensor... except for one of the points. This causes the motor to keep cutting out when using pedal assist, I'm able to get the motor to run constantly when using the throttle.

I can't see anything obviously wrong with that particular point (everything is clean, it seems flush with the disc like all the others), and the distance between disc and sensor seems consistent as the disc turns.

Any tips on what I can try to fix this? I've also reached out to the supplier of the kit but they are very slow in responding and these seem like standard components so I'm guessing some of the people here may know what to do.

Here's a video of the PAS sensor in action that I uploaded to youtube:

Thanks in advance!

 

[Nealh]

The only thing possible I can think of is the magnet has been put in wrongly as they have a north & south pole, try prying it out and reversing the face.
Alternately one can use another small magnet to see the reaction compared to the others and see if it attracts or pushes it away.

 

[Chees]

Genius. I moved the connector to the other side and it lights up for that one point only when rotating backwards. I'm going to try turning that magnet around but I wonder how to make sure it stays there afterwards? Might need a dab of superglue I guess.

 

[vfr400]

First thought is that a magnet is the wrong way round. If that's not it, there are settings in the LCD for what type of PAS you have, and, IIRC, another one for its sensitivity.

 

[Chees]

@Nealh @vfr400 bingo! it turns out that you can push the magnets out pretty easily and there's no adhesive or anything. I just flipped it around and slid it back in (it's pretty tight so unlikely to fall out by itself) and the sensor is lighting up at the right times now. Will take it for a ride later to test that it's all working.

Thanks for the help guys!

 

[vfr400]

@Nealh @vfr400 bingo! it turns out that you can push the magnets out pretty easily and there's no adhesive or anything. I just flipped it around and slid it back in (it's pretty tight so unlikely to fall out by itself) and the sensor is lighting up at the right times now. Will take it for a ride later to test that it's all working.

Thanks for the help guys!

I had a magnet fall out once. It made the bike unrideable. You wouldn't think that something so small could make such a big difference.

Yours is the second one with a wrong magnet in the last few weeks. Before that, I'd only seen heard of a couple in ten years.