Broken throttle? Goes full speed.

Hi I just wanted to ask for anyone's thoughts before I go ahead and buy a new throttle.

I have a 48v thumb throttle for my ebike which I got with my ebike kit back in 2011 so it has had quite a bit of use on it after all these years.

The other day I was going full throttle down the road and when I let go of the throttle, the motor as expected started to slow down but a few second later when I pushed down slightly on the throttle again it suddenly picked up full speed so I let go of the throttle but it continued to go full speed so I slammed down on the brakes (I don't have electrical brakes) and that brought the bike to skidding halt and I disconnected the battery quickly.

On further inspection it does not seem any wires have shorted between the controller and the throttle but the second I plug in the battery, the motor wants to go full speed.

I was wondering if these throttles eventually brake? Is it just in need a new throttle and nothing wrong with the motor hopefully?

Of course nothing lasts forever... but the electronic components of a hall sensor throttle are fairly robust. As long as you keep it high and dry. :wink: The biggest issue for a thumb throttle may be the snapping action of a quick return to closed position if allowed. A quick check to isolate the problem would be to remove the throttle and see if the issue disappears. If it does the throttle most likely will be the cause.(see troubleshooting below)

With the relatively low cost of a replacement, it would be a reasonable choice to eliminate the issue.

That said, a hall sensor throttle will also go to full output if it loses its ground wire connection. So not just a short can be involved. It would connect to the sensor as shown below...




I would certainly check this first (hall sensor ground leg to batt negative) before ordering. When open check for any mechanical issues also, such as a dislocated magnet or the sensor itself out of position.







For intensive information on a hall sensor throttle, as well as tips on troubleshooting, disassembly and mods, ETC... See this thread...

https://electricbike.com/forum/foru...r-throttle-operation-testing-and-modification

I am a strong advocate for brake cutoff switches. Please reconsider and as always... stay safe.



Regards,
T.C.

Buy at least 1 or 2 extras to have on hand, since they're so cheap. They're one of the easiest things to break on an ebike, so it's good to have spares.

Hi thank you so much for the detailed response. I opened up the throttle to see if the ground connection was loose and it was. In fact the other 2 solder connections to the sensor were about to break and the middle pin (blue wire) was already broken.
So I suppose I could buy a new sensor and just solder it in? Or perhaps just pay a bit more to get a new throttle but your both right at least its the easiest & cheapest thing to replace!

Only problem now is the allen bolt that holds my brake lever is rusted and now stripped and I can't remove it to replace the throttle but of course that is just another problem!

I will look into replacing the sensor.

Thank you!!

I've had the exact problem you had.

My problem was moisture.
Its wise to buy 2 spare throttles.

If moisture got onto the connector of the throttle, or it may have been the wiring exit from throttle, then the throttle would go full on all the time which always seemed to happen when I was already at full throttle. I would let go of throttle and it would still go full throttle, but if I used the throttle it would cut the power. I would blow on the connector and it would work half the time, but I could work with full on and full off.

Full on all the time, no matter what, then hopefully there is a way to cut power, I know a few times I would have to pull the battery connector if my bike fell and went wide open throttle (wot).


I personally like the universal left or right, 130X

All throttles page
https://evfittinggreentime.aliexpress.com/store/group/Throttle-gas-handle/313864_251589097.html?spm=a2g0o.store_home.pcShopHead_11248317.1_6

Get a quality waterproof throttle (I have domino, magura might be fine too, lower quality though). These $5 chinese jobs aren't waterproofed at all. Also hook up an e-brake, at least the rear one. It will still allow you to do burnouts with rear wheel while holding front brake.

the most common problem that causes full throttle is simply a broken ground wire somewhere between throttle and controller. (can be broken inside the controller too, ground wire broken off the pcb)

so check that first before anything else. it's a very easy fix if so.



the next most common is a magnet coming off the spot it's glued to inside the throttle. this can be fixed easily enough, but getting the throttle apart and back togehter without breaking anything else may not be.

GT877 said:

... and the middle pin (blue wire) was already broken.

Click to expand...

The middle sensor leg/wire IS the ground. So it makes perfect sense. :wink:

GT877 said:

So I suppose I could buy a new sensor and just solder it in?

Click to expand...

Odds are just remaking the sensor's wiring connections may be all you need to do! If you are set-up to solder, I'd give it a go. (at the least would be good practice)
Remember to keep the heat on the legs to a minimum. (time/temp) Heat shrink tubing on the legs/wiring to prevent shorts.
And from your description, I would certainly concentrate on some type of strain relief. As it sounds like your wiring may be moving around a bit. Tie a knot in the cable, hot glue down... something to secure it properly. If your worried about water egress, after the repair and testing would be the time to pot it all in silicone caulk.

GT877 said:

Only problem now is the allen bolt that holds my brake lever is rusted and now stripped and I can't remove it to replace the throttle but of course that is just another problem!

Click to expand...

Always something...

Here's something for inspiration!









:lol: But seriously... Room to get vice grips on? Cut off with a Dremel cut-off wheel...

Thanks all for the comments on this.

So the middle pin is the ground, that makes perfect sense then! I checked the wiring everywhere else and it seems these broken pins at the sensor are the only problem.
The magnet is still firmly in place where it should be so that is good.

The sensor part number reads SX49E 108 and is absolutely tiny but I've bought SS49E sensors and hopefully will work the same. Soldering this is going to be a bit fiddly I imagine but will give it my best!

Thank you so much for the suggestion on sealing off the throttle from water and also securing the sensor from vibration/movement, I had not thought of either of these problems before but will definitely do this.
I am using the bike almost on a daily basis and half of the days this winter have been through a lot of rain!

As for the brake lever, unfortunately the allen bolt is a sunk one so no way to grip it or grind it down, perhaps drilling it out is my best bet! If I wreck the threads then I suppose I can just use a nut with a longer bolt to clamp it in future.
I am also looking at buying an electrical brake lever (Perhaps to replace the one with the stuck bolt)

That tool expectations picture sums it up perfectly! I am printing that out and posting it on my wall to remember haha thanks

I will give a quick update in a few days once I've replaced the sensor.

Thanks again!

Quick Update! I did attempt to solder in a new sensor despite it's tiny size but I did a pretty bad job at it and then could not get it properly seated afterwards and so when connected to the battery the motor would immediately startup but at a lower speed this time.
I decided to just go ahead and buy a new throttle since they are fairly cheap. All works great now and I have sealed the edges of the throttle box with silicone sealant to help keep it dry in wet weather.

Thanks again everyone for the help!

Glad to hear you got it sorted out. Job well done! :thumb: