Torque Sensor Strange Behaviour

[S.Giles]

Hello,

I have two identical Engwe L20 Boost ebikes (20'' fat tyres, step through design). One of them has 750 miles on the clock, the other 2500 miles.

The higher mileage one has recently developed a problem with the torque sensor. It has become very sensitive to pedal input, to the point where it is even possible to ghost pedal. Picking up the rear wheel and turning the pedals by hand, even slowly, causes the motor to spin up to full speed (21mph indicated on the display). Also, when riding the bike, acceleration from stationary is not smooth (a slight delay, followed by full power).

I would very much appreciate it if anyone could throw some light on this. Is this a known fault condition? Luckily, I have a spare torque sensor, but don't yet have all the tools necessary to fit it.

(Thinking about it whilst writing this, I guess that unplugging the torque sensor from the controller and cleaning the contacts might be a prudent first move.)

Many thanks,

Steve

 

[S.Giles]

Ok, I was able to experiment with what I have and answer some of my questions.

I unplugged the faulty torque sensor (which had become so sensitive, it would even activate the motor with the chain off) and electrically connected the spare one. Using two wrenches I was able to apply enough torsion to activate the motor and spin the wheel. The response seemed to be normal.

So now all I have to do is physically fit the new torque sensor to the bike and I should be good to go.

I'd still like to know how common torque sensor malfunctions are though. Should I obtain another spare, so that it's ready for next time this happens? The bike is less than two years old.

Steve

 

[harryS]

Nice work on analyzing the problem. I don;t own an Engwe, but it appears the failure is common enough that they published a video on torque sensor replacement. And it appears they will send out spares under warranty, Is that how you got your spare?

Well, I would get another one while I could for insurance.

 

[S.Giles]

Thank you for the link Harry. I hadn't seen that video. (BTW, why do they advise disconnecting the motor? With the battery disconnected, there's no energy in the system.)

I can get the cranks off easily enough, but loosening the nut that holds the chainring on is a challenge. I have the tool to do it, but it doesn't fit in my drill. I could use a 24mm wrench, but I don't have one. (yes, I do know it's reverse threaded!

Engwe sent the torque sensor out to me free of charge over a year ago in response to an intermittent problem I was having with the pedal assistance shutting down at random times. I wasn't convinced the torque sensor was the culprit, so I never got around to fitting it. It's coming in handy now though, especially since the bike is now out of warranty.

Thanks for the reply!

Steve

 

[PedalUma]

If it has a drive side lock-ring those are often reverse threaded so they don't go flying off while you are pedaling. I am not familiar with this bike.