Pedal assist not working

alan from eston

Finding my (electric) wheels
Oct 28, 2014
10
1
71
As mentioned in a previous thread i have just fitted front wheel e kits to mine and the wifes bikes and all was working ok, I have now tidied up the wiring and got the controllers fitted in the carrier boxes but now one of the bikes has lost pedal assist.
Everything else is working ok the led meter works and the throttle and brake switches are all ok, I double checked all the connections and all are ok so i swapped the controllers to elimate that but still the same, so i assume the pedal assist sensor is faulty, are there any other tests i can carry out to check the pedal sensor or is it likely the sensor has failed after barely a couple of miles use.
 

alan from eston

Finding my (electric) wheels
Oct 28, 2014
10
1
71
I've just checked continuity on the sensor wires and on the red and black pos and neg wires i got zero, so i checked on the one that works ok and got a reading of 17.93k ohms so it looks like a broken wire. does this sound about right?
 

Kinninvie

Esteemed Pedelecer
Oct 5, 2013
891
401
Teesdale,England
Do you have a photo of the sensor?
I had one fail after 60 miles from new.
mine

 

JamesW

Esteemed Pedelecer
Nov 17, 2014
492
72
38
I had similar problems but mine was not an electrical issue but a mechanical mounting issue. If the PAS detector is too far from the disc it doesn't detect the rotation, bending the metal bracket holding it and checking the alignment (with the bike upside down) is a good way of checking)
The different readings were done on the bikes? you didn't have the disc holding the (magnets?) in different positions relative to the sensor did you as I get the feeling that this can affect your DMM measurement - it certainly did for me!

James
 
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alan from eston

Finding my (electric) wheels
Oct 28, 2014
10
1
71
Right i'm back with a update,
Pro rider Mobility sent me a new pedal sensor that solved the issue, when i checked the old one i found one of the wires had snapped inside the sensor but due to the fragile connectors it could not be repaired as the other connectors snapped off while the thing was dismantled cos it is full of sealant making it difficult to strip.
I added some hot glue to the cable entry on the new one to seal and reinforce the cable to take the strain.
So the bikes are now working ok and me and the wife can now get out on the bikes for exercise and make light work of the hills.
 

Charliefox

Esteemed Pedelecer
Feb 11, 2015
257
62
76
Culloden Moor Inverness
Right i'm back with a update,
Pro rider Mobility sent me a new pedal sensor that solved the issue, when i checked the old one i found one of the wires had snapped inside the sensor but due to the fragile connectors it could not be repaired as the other connectors snapped off while the thing was dismantled cos it is full of sealant making it difficult to strip.
I added some hot glue to the cable entry on the new one to seal and reinforce the cable to take the strain.
So the bikes are now working ok and me and the wife can now get out on the bikes for exercise and make light work of the hills.
Where you really bothered when the pedal sensor stopped working? I have an old Powerbyke and the sensor in that is a magnet glued to the inside of the bottom bracket shell and another stuck on the crank axle itself. It is only used to tell when the pedal is moving.This is to save the motor from the stress of starting from 0 mph.(another sensor! in a band brake fitted to the NS side of the rear wheel can sense the speed) Well it was early days back in 2000! I use the throttle all the time and got used to squeezing it lightly against it's fixed part to maintain a constant speed over rough roads.Holding the throttle as on a motorcycle gave me a sore hand after a while. I am hoping to get away without the pedal sensor on an MTB conversion and just use the throttle on the hills.
 
D

Deleted member 4366

Guest
Modern bikes have adjustable power from the pedal sensor, so the pedal sensor works like a cruise control. It's much easier than a throttle for normal riding. The throttle is still useful for the following circumstances:
  • Getting a good start at the traffic lights, onto a roundabout or crossing a main road.
  • When going through floods
  • When going over slippery surfaces
  • When going through deep mud
  • When heavy shopping or other awkward load impedes your pedalling
  • When you've fallen off and injured yourself so you can't pedal
  • When your crank comes loose
  • When you want a rest from pedalling after climbing a steep hill
  • When your bum hurts during a long ride, you can take your weight on your feet for a bit while circulation is restored
  • If you have some physical impediment that makes it difficult to pedal
  • When you want to show off that you have an electric bike
  • When you want to test your motor

That's why I prefer to have one. Anybody else feel free to add to the list.
 
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Perseus

Esteemed Pedelecer
Oct 15, 2015
350
17
68
Modern bikes have adjustable power from the pedal sensor, so the pedal sensor works like a cruise control. It's much easier than a throttle for normal riding. The throttle is still useful for the following circumstances:
  • Getting a good start at the traffic lights, onto a roundabout or crossing a main road.
  • When going through floods
  • When going over slippery surfaces
  • When going through deep mud
  • When heavy shopping or other awkward load impedes your pedalling
  • When you've fallen off and injured yourself so you can't pedal
  • When your crank comes loose
  • When you want a rest from pedalling after climbing a steep hill
  • When your bum hurts during a long ride, you can take your weight on your feet for a bit while circulation is restored
  • If you have some physical impediment that makes it difficult to pedal
  • When you want to show off that you have an electric bike
  • When you want to test your motor

That's why I prefer to have one. Anybody else feel free to add to the list.
When the mechnical pedalling ceases to work. Like now!
 

Fordulike

Esteemed Pedelecer
Feb 26, 2010
3,494
1,341
Tyne and Wear
When the mechnical pedalling ceases to work. Like now!
Try the following:

  • Clean the pedal sensor disc and the little receiver unit with some contact cleaner.
  • If it still fails to operate when turning crank, check that the sensor disc isn't damaged, and that it runs true, close to the receiver unit.
 

Slimjim

Pedelecer
Aug 28, 2016
56
3
46
Doncaster
Apologies for hijacking this post, and thanks in advance for any advice. I am in the process of fitting my brother's two year old Cytronex kit to a different bike. The kit is prewired, and intact, apart from missing the crank magnets.

The kit has the ni-mh bottle battery, which is reported as fully charged (by the correct charger) after a three hour top up.

Also fitted/wired are front and rear lights, which work from the second thumb switch.

Some Cytronex kits have a bike computer, buy this one doesn't, and I can't see a spare/unused plug for one in the harness.

There are two 'hall effect' sensors, one red and one black.
Also a reed switch (I think it is - small black tubular sensor) for brake activation. I don't have the brake lever magnet, and will be fitting this kit to a bike with hydraulic brakes.

I've been told that the black hall effect is for a wheel speed sensor, and it is wired through the harness to the motor controller.

The red hall effect is apparently the pedal-assist sensor.

The motor is a 180W Tongxin front hub, 175rpm, 29 inch wheel.

I have temporarily fitted the kit to the intended bike.
I only had a couple of spare 'wheel magnets' from old bike computers, so I taped these 180 degrees apart to the small chainring, and taped the red sensor to the frame/chainstay.

When I switch the system on (thumb button shows red light), and spin the cranks, after a few revolutions the front hub will start to turn, but only got half a rev. Then cuts out. Then cuts in. And out. Etc for a few seconds. Then stops reacting.

I've tried various combinations of repeating this test with a magnet against the brake sensor (one orientation stops the motor turning at all, the other orientation results in the same on/off clunking). And also with and without a spoke magnet on the back wheel, so that it spins past the black sensor when I turn the cranks.

The effect is always the same on/off for a few seconds, then nothing.

I don't have a user manual unfortunately, and can't find a wiring diagram online.

My brother thinks I might need a new red pedal-assist sensor. Possibly I also need to fit the correct number of magnets (although obviously I can spin the cranks faster to get a higher frequency pulse from just two magnets).

Any suggestions for how to test the red sensor? The rubber sheath has pulled back from the sensor, exposing three coloured wires, but their insulation seems intact. If i hold them straight I seem to get a note immediate response, but the wheel still atops after a few turns so I can't prove this.

Also, should the black sensor be mounted at the front wheel - I.e. does the motor controller use a feedback loop to check motor speed, hence if it's not measuring the correct motor speed (because the black sensor is on the un-motored wheel), does the controller error?

Also, the brake lever sensor doesn't seem to need a magnet near it to let the motor drive, unless that just worked because I had placed the magnet against it in the wing orientation?

Any advice on the logic of the system would be very useful, before I spend money on a new red sensor.

I'll order some magnets, and continue to try with the black sensor on the motored front wheel.

Thanks, Adam.
 

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