What happened ... long dead ebike resurrects

Hello,

I have a 36v rear hub e-bike that has not worked since it stopped all of a sudden in 2016.

As I got further into taking it apart and testing connections on it, I powered it up with the throttle connector disconnected then reconnected it.
The motor started to run !!
(Doubly surprising since this bike is set up so that you *have to* pedal to run the motor)

So I repeated the 'experiment' and fiddled with throttle and now : it works !!
Hooray!

*Except* that it is as though the throttle is on all the time now, so you get pedal assist when you pedal, regardless of throttle position.

Would anyone have any idea what has happened here?
I'm feeling fairly confident that I can just replace the throttle now right?

Thanks for looking

Keep working on those loose connections. Sounds like your throttle is shorted out now.

If "do you get pedal assist regardless of throttle position" was a question, yes, sometimes you do depending on the system. Some have a button or switch that changes from one mode to the other, but again some don't. Does it keep running when you let off the throttle?

Thanks Dan and Voltron,

Voltron said:

If "do you get pedal assist regardless of throttle position" was a question, yes, sometimes you do depending on the system. Some have a button or switch that changes from one mode to the other, but again some don't. Does it keep running when you let off the throttle?

Click to expand...

Sorry : there was a typo, now corrected, it's " *so* you get pedal assist ..."
I have had mine completely dismantled now ( well, except the rear wheel / hub ) so I know there isn't a button.

What happened first was that, whilst exploring with a multimeter and with the battery on, I disconnected the 5 wire connector from controller to throttle ( which is a twist on/off with 3 LEDs "Motor" "Full" "Empty" ).
Then when I reconnected it, the motor ran continuously.
This is the biggest mystery because it should never run without pedalling on this model which has the magnetic sensors next to the gear cassette on the rear wheel.

I repeated the same procedure out of curiosity but also found that it seemed to have "cured" the problem : the bike had been "lights on but no motor" since 2016. Now, it works albeit with a seemingly shorted throttle.

Since its failure, first-up I took it to its shop (obviously, not a great shop) of origin who really only took it apart and said "it doesn't work". I then considered returning it or parts of it to its manufacturer in Bolzano, North East Italy. But that is impossibly expensive from here - hundreds of Euros, especially since they insisted I send the whole thing!

So out of necessity but also happily ( as I have the time atm ), I am committed to diagnosing it myself and repairing it ... subject to an early viability check of course!

So in short : there was the 'big mystery', how could it run upended on my table without pedalling?
It doesn't need to be solved now, since dis-/-reconnecting that connector with power on is totally abnormal, I was just curious how such a thing could happen.

The bike ( which I threw back together for a very short road test ) runs , with an apparently shorted throttle.
It is also very whine-y from the motor and not pulling strongly but I put that down to the old battery ( lead acid X 3 but still showing 40.5v full ). But that is another story. I will get anther battery as soon as I am sure the rest is ok or realistically repairable.

Best wishes !

Sounds like oxidation on the connectors. Just plugging and unplugging them a few times will scrape the pins down to clean metal...

Savoyard said:

What happened first was that, whilst exploring with a multimeter and with the battery on, I disconnected the 5 wire connector from controller to throttle ( which is a twist on/off with 3 LEDs "Motor" "Full" "Empty" ).
Then when I reconnected it, the motor ran continuously.

Click to expand...

If ground is broken on a throttle, it can float in voltage to values taht cause this.

Sounds now like you have the positive and retuning positive wire of the throttle shorted, giving a full throttle signal back to the controller.

The fix might be replacing that 5 pin plug. or the problem could be in the throttle itself.

Spinningmagnets, Amberwolf, Dan and Voltron,

I do want to thank you sincerely for your tips, I really appreciate it.
Plainly, I am an absolute noob.
I will go ahead and check all the connectors.

My progress has been delayed by a back problem ( I write this from a horizontal position ! ) ... but I do have a follow up question about the throttle.

It feels mechanically a bit broken so I want a replacement.
The manufacturers part being US$50, I have been searching around and getting the feeling that I am not going to find a compatible part.
Mine is a twist throttle with 3 indicator LEDs. There are 5 wires. It's easy to find 5 wire replacement throttles, but those 5 wires do very different things on all the models I've found so far online.

So my question is : do you have any idea where I might find a matching and/or compatible one?
Or if not, can I test my theory that it is faulty by wiring in a simple switch to replace the throttle?
If that confirms the fault, then it seems I would have no alternative other than to buy this very expensive replacement . Unless I can find an e-bike breakers yard!