Pedal assist doesn’t work anymore on TODO Mountain Rider E-Bike, please help

Hi,

A few months ago, I bought a cheap electric bike off eBay, the "TODO Mountain Rider E-Bike", for the price of 990 AUD, shipping included to Tasmania, Australia (from New South Wales, Australia).

It comes with a geared 250W rear-hub motor (Bafang I think), a Shimano Tourney drivetrain and a KT-LCD3 display with control buttons. The display is fully preconfigured out-of-the-box for that specific bike, so I never had to adjust any of the settings.

I’ve been reasonably happy with the bike, given the price, for the first 500 km or so. Until now.

Normally, the hub motor/assist function would activate either when I pedal, or when I push the assist switch. Now, the assist function only works when I push the switch, NOT when I pedal, like it used to. It happened overnight and I don’t remember doing anything to the bike other than maybe dropping it on its side by accident once.

The fact that the hub motor and the assist function still work normally when I push the switch makes me think that it’s not a software issue, and not an issue with the hub motor, but maybe a sensor issue? As in: the control box and LCD don’t seem to detect the pedalling and thus don’t activate the assist. That’s my best assumption anyway.

Unfortunately, because it’s a cheapo, Chinese made, no-name kind of product, there’s no official support for it. The manual is useless. I tried fiddling around with the cabling and cleaning the little part next to the derailleur (see red arrow on photo below), to no avail, and I don’t really know what else to try.



I have the black version, but you can see details here: https://www.ebay.com.au/itm/EBIKE-ELECTRIC-BIKE-36V-9Ah-250W-MOTOR-PEDAL-ASSIST-SHIMANO-GEAR-MTB-PAS-BICY/362326076778?hash=item545c512d6a:g:UmwAAOSw7HhcEgOb&frcectupt=true






Yes, I know, shouldn’t have gone for the cheap stuff, but if this is fixable, then I believe it is still a decent purchase.

Anyway, any help would be hugely appreciated

Cheers!

Just for clarification, where is the "switch" on your photo? I see a thumb throttle; is that what you mean? I can confirm that the first picture is the pedal assist sensor (PAS) that should trigger assist. I'd check connections first, by unplugging and plugging back the wires on the harness that have 3 wires to make sure something didn't come loose there.

If it works by throttle, but not PAS, its nearly always going to be a wire problem, plug problem, etc. That thing on the crank is the PAS sensor. Too far from the magnet ring that activates the switch in the sensor could be the problem, but it looks ok. Trace that wire, and see if the plug contacts are all the way into the housings, or are breaking loose, or have a cut wire along the way.

Hi E-HP and dogman dan, thanks for the quick replies, and sorry for my late reply, didn’t have access to the bike for a while.

To answer your question, yes I meant the thumb throttle by "switch".

I just did the following:
- check that all magnets are on the disk (they are)
- clean the disk+magnets
- clean the sensor
- check if the sensor has a LED (it doesn’t)
- open the controller box (everything looks healthy inside)
- put the rear of the bike on an improvised stand and test the wires with a voltmeter (steady 5V, even when pedalling)

If I understand correctly, it must be a PAS sensor issue. Any advice on where to get the correct one? There seems to be 10 magnets on the disc, wouldn’t want to get the wrong one!

Weirdly, the wires on the sensor cable are red/green/yellow on one side and red/yellow/blue on the other.


My creative mounting system (camping stove on one side, old Playstation 3 on the other!)




Sensor cable, wires are weird colours.


If you’re curious, inside the controller box.

Thanks again!

Looks like a LiShui (LS) controller like my old Fusin kit, probably a Kingmeter display.

Totally normal that the wire colors don't match.


The most likely problem is that either the sensor got water in it and failed, or that a connection is broken between the controller and the sensor.

Which wire has the 5V on it? And exactly where are you measuring (where are the voltmeter probes)? There should be 5v on one wire (power), 0v on another (ground), and a changing voltage on the third as the magnets pass the sensor.

If there is no changing voltage, try taking a single magnet from something else and waving it past the sensor while you measure. If it works, then the sensor has been bent or mvoed away from the magnet ring, ro the ring away from the sensor, and that's easy to fix.

If it's stuck at 5v all the time, then most likely either the senosr ahs failed (it should ground the signal line as magnets pass it), or the wire is broken somewhere between the sensor and the point you're measuring. Try probing the wire close to the sensor, by poking the pointy tip of the probe thru the insulation into the wire itself. (you might have to gently cut away the black sheath around the wires to reach it).

Yeah nah, no flipping on the 5V signal, nor on the 4.3V one. I also tried passing a bigger magnet in front of the sensor to no avail. I put the probes in all possible combinations in order to determine which signal does what. I get 5V on one, 4.3V on another (power?) and 0V on the last. Poked through the wires close to the sensor, same result.

I’m in Australia. I’ll order a new magnet and report on it (might be a while...). I just hope the new magnet fits, but I’m guessing it’s standardised.

Thanks again for your help.