Help! E-bike not sensing pedaling

[technopedler]

I purchased a custom built e-bike 2 years ago from someone (I can no longer get in touch with them though) and it's been fairly reliable. Recently however, it has stopped assisting when I pedal. It happened during a cycle journey and it was working fine and then just suddenly stopped while I was midway up a hill. The battery had plenty of charge and the motor is fine as well because I can use the thumb throttle which makes it work. Managed to get home and put the bike on a workstand. Using my hands, I get no power assistance at all when I pedal but it gives power on the throttle.

I don't fully understand how the pedal sensor works but it seems intact and without damage (picture of it is attached). I opened up the little bag housing the controller (picture also attached). There's a bunch of wires none of which I know what they do, but the ones that were connected, I checked to make sure they were pushed in okay. There doesn't appear to be any loose wires that have come undone. The few loose wires have hot glue over the connector in a way to cap them off as they are unused (so I know they were not connected).

Can anyone help me work out how to diagnose this issue and figure out how to replace the pedal sensor if that is what is wrong?

Thanks in advance

 

[vfr400]

The pedal sensor has a magnet ring and a hall sensor arrangement, as each magnet passes the sensor, it gives a 5v pulse. Some of those devices have a little red LED that's on when the LCD switches on, then flashes when you pedal. If it's off, then there is no power to it. If it's on but doesn't flash, it's broken.

If it doesn't have an LED you have to test it with a voltmeter by applying 5 v to the red and black wires, then measure between the third wire and the black while you turn the pedal very slowly, to see the 5v pulse 12 times each revolution. If you know how, you can lift the signal wire pin from the connector to measure it, then you can use the controller to apply the 5v through the other two wires to power it.

 

[technopedler]

So is the pedal sensor and magnets housed within this thing?

 

[vfr400]

Yes. Remove the pedal arm with a crank puller, then the sensor can be pulled off. There's a screw on the inside that allows you to separate the two halves.

Before pulling it off and after the pedal arm is removed, you can observe whether the inner part is turning. It might be jammed with dirt. There are flutes that grip the pedal shaft. If the sensor jams, they wear and lose grip, in which case you have to find a way to help them grip, like silicone sealant, hot melt glue, tape or similar, or buy a new one.