Help! PAS does not work

tuesday123

Finding my (electric) wheels
Dec 14, 2019
8
2
Hi there.
Please I need help for my E bike bike...
It is with build in controller and everything works instead of the PAS. Its actually work when I start pedal but for just 1sec and then stops.
I change the PAS sensor but is still the same...
Does anyone know what the problem could be?

Thank you very much!
 

Wisper Bikes

Trade Member
Apr 11, 2007
5,794
1,771
65
Sevenoaks Kent
Have you checked the distance between the magnets on the disc and the sensor? If it's too big the sensor will not pick up the signal from the magnets, for the same reason make sure that the magnets are clean.
 
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KirstinS

Esteemed Pedelecer
Apr 5, 2011
3,209
886
Brighton
Whisper answer is most likely

If you have changed the sensor but cannot get the distance close enough I have read of those who have added extra magnets to the PAS ring



Doubtful this is the issue tbh but hey, I'll chuck it out there
 

Nealh

Esteemed Pedelecer
Aug 7, 2014
11,942
4,632
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West Sx RH
Which PAS are you using ?
Post a pic or two of the sensor mounted.
 
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tuesday123

Finding my (electric) wheels
Dec 14, 2019
8
2
Thank you very much for your reply. I will try to ad extra magnets and to get the distance closer.
Regards
 
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KirstinS

Esteemed Pedelecer
Apr 5, 2011
3,209
886
Brighton
Thank you very much for your reply. I will try to ad extra magnets and to get the distance closer.
Regards
When you hear hoof beats think horses not zebra as they say! Best ignore my post on that basis and diagnose issue properly and in order

Getting them closer is most likely and Nealh is right. We should see photos first before any"zebra" magnet solutions
 
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Nealh

Esteemed Pedelecer
Aug 7, 2014
11,942
4,632
57
West Sx RH
It may be the angle /degree the sensor /plate is set at, try and see if you can position it so it sits more on a horizontal plain.
If it runs in testing it should run in real time use.
When you lift the bike rear up the sensor plain changes a bit and will be nearer the horizontal.
 

Kwozzymodo

Pedelecer
Sep 9, 2017
150
29
59
Lincolnshire
Are you sure the magnet disc is spinning when you pedal? If it is loose on the axle, it might be getting stuck when you pedal and therefore won’t be sending any pulse to the controller.
 

Kwozzymodo

Pedelecer
Sep 9, 2017
150
29
59
Lincolnshire
Just looked at the picture - is that disc the right way around? My eyes may be playing tricks but it looks like the magnets are facing outwards and not towards the sensor.
 

Nealh

Esteemed Pedelecer
Aug 7, 2014
11,942
4,632
57
West Sx RH
Mag disc may still be orientated wrong so flipping it won't hurt to try.
I have had one of those cheapy thin ones where the magnets are set in an almost blind hole barring a pin prick of a hole on the rear.
 
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Kwozzymodo

Pedelecer
Sep 9, 2017
150
29
59
Lincolnshire
I am curious. I dug out some magnet discs with the arrows indicating rotation. The surface area of the magnets is larger on one side of the disc than the other (per nealh comment above). Aside from making sure the magnets are facing the sensor, why the arrows? Surely if the magnets are rotating one way or the other they are still generating the same strength magnetic field for the same exposed surface area of each magnet?
 

harrys

Pedelecer
Dec 1, 2016
170
22
69
Chicago, USA
PAS sensors are designed so that if you rotate the crank backwards, they can detect it and not run the bike. THey do this by detecting how how your magents are positioned as the pass the sensor.

So flipping the disk the wrong way when you install it is the same as spining the pedals backwards.

In addition, some of us installers will flip the sensor, or change which side of the axle when they install it, which also can complicate getting PAS to work right.