Hello and help please!

[Zeffer]

That did it. The wheel is turning! So, have you a good link for buying a new sensor? I can't fix it by putting a magnet on the back of it?!

 

[Alan Quay]

Depends on how its fixed on. Normally, it's on a bracket that fits into the bottom bracket retaining ring

To change it, you will need to remove the crank arm, then the ring. Again, pictures will help....

 

[Alan Quay]

Like this?

http://pages.ebay.com/link/?nav=item.view&id=230964430999&alt=web

 

[Zeffer]

It's just as you say. Will order one later and let everyone know how I get on with the repair.

Thanks to you both for guiding me through the process. Let's hope this sorts it.

 

[Alan Quay]

Glad to be of assistance.

 

[Zeffer]

Best check. Will this one do? The gold coloured mounting ring is identical but mine is a black sensor. I assume they all do the same job but I want a reliable one!

http://www.ebay.co.uk/itm/Electric-Bicycle-Power-Pedal-Assist-Sensor-for-24V-and-36V-8-Magnet-PAS-/321499168113?pt=UK_sportsleisure_cycling_bikeparts_SR&hash=item4adad7fd71

 

[Deleted member 4366]

The yellow wire should switch on and off with 4.7v five times a second when pedalling normally. To test it, you have to rotate the pedals very slowly. I thought that the red LED should flash when you turn the pedals. Does that happen on your wife's bike?

Some bikes have extra components in the pedal sensor that convert the flashing into a continuous voltage like a throttle signal, so you need to measure between the yellow and black when somebody turns the pedals at normal speed too to see if the voltage rises.

Edit: As you already tried shorting red to yellow, I don't think yours is like that.

The pedal sensors are normally very reliable unless you pulled/broke the wires.

 

[Deleted member 4366]

What did you do to make the motor turn?

 

[Zeffer]

It was a short between yellow and black that made the motor turn. Had to tap quickly with the paper clip I was using but it worked. Will check my wife's bike tomorrow to see if the LED on the sensor flashes.

The wires have been untouched and visually seem fine. I rode to the shops and when I came out the motor wouldn't come on. Seems so odd.

 

[Deleted member 4366]

Check whether it pulses between yellow and black on each side of the connection to the controller. It might just be a bad connection or bad crimp on the pins.

 

[Zeffer]

Thanks for the tip - I'll give it a go tonight after work before making any purchases.

 

[Zeffer]

Small update. The LED does flash on my wife's bike but not mine.

 

[Zeffer]

Check whether it pulses between yellow and black on each side of the connection to the controller. It might just be a bad connection or bad crimp on the pins.

No pulses both sides of the connection. Just a steady 4.7 volts.

 

[Zeffer]

Managed to unscrew my sensor without totally dismantling the crank. It's a DH Sensor - King Meter: http://www.king-meter.com/products.php?action=detail&id=41

 

[Deleted member 4366]

Any normal pedal sensor should work.

 

[Zeffer]

Ok, I'll order one now. Will I be able to keep my magnet disc or should I change that as well?

 

[Zeffer]

Another question. Does it matter that mine is on the side of the chain set whereas some photos show them on the other side? Are there different sensors for each side or does it not matter?

 

[Deleted member 4366]

You can fit them to either side. You just flip the magnet disc for each side. You can probably use your existing magnet disc, but they come as a pair anyway,

 

[Zeffer]

Thank you. Out of interest how does it know if you're pedalling backwards? Oh and my disc has more magnets than the ones on eBay, so hopefully it won't matter.

 

[Deleted member 4366]

It knows by the direction of the magnetic field. That's why you have to flip the magnet disc if you change sides. Having a disc with more magnets is the same as pedalling faster.