How to fix a blown throttle for about 25p

[Deleted member 4366]

I had to repair a throttle on a bike where it had been shorted to 36v, so the hall sensor was blown. I thought I'd make a how to do it because it's a common problem.

All throttles are more or less the same whether thumb, half or full-width. There's a hall sensor inside with a magnet either side on the bit that you twist. The magnets are orientated the opposite way round, so at zero throttle, you have the low magnet against the sensor, and at full throttle, the high magnet is against it. If you take the magnets away, you get half-throttle.

Whichever type you have, you have to dismantle them to get to the sensor. After removing it from the handlebars, you'll see some barbs on the inside that stop it from coming apart. you need several screwdrivers to hold them all back at the same time. It helps if you can get a friend to wedge a screwdriver between the two parts and twists it to put pressure on the barbs, that way they stay lifted until you lift the last one and it'll pop apart. Before pulling it right out, make a note of where/how the spring is located.

Here's my one taken apart. The barbs are on that raised rim on the bottom part. The top part is the bit you twist. You can just see the two magnets connected by a strip of metal in the top part. Some don't have the metal strip:



The reason that you have to take it apart is that the hall sensor is under a little panel that you can't remove until the halves are separated.

 

[John F]

This is very interesting. I'm having trouble with my throttle. Rode through a downpour last week, and now it's playing up. Any ideas for weatherproofing throttles?!

 

[Deleted member 4366]

Now with the panel removed, you can see the three wires that go to the hall sensor, which sits in a slot,



Here it is with the hall sensor pulled out and ready to be replaced by a new one. The designation is SS49E. They cost a few pence:
10 pcs Hall element 49E OH49E SS49E linear Sensor AB | eBay



New one soldered in. You need to heatshrink sleeve the outer two because they sit close together. Shrink-sleeve from Maplin.

 

[Deleted member 4366]

Finally re-assemble. You have to put the spring in place, then rotate the magnets round to the sensor before pushing it all the way past the barbs. That's it.



Here's a thumb-throttle that has extra wires for the LEDs and switch, but the hall sensor is the same.

 

[D C]

This is very interesting. I'm having trouble with my throttle. Rode through a downpour last week, and now it's playing up. Any ideas for weatherproofing throttles?!

The throttle does seem to be the weak link in the chain as regards weatherproofing and I must address this soon.
Maybe something involving a rubber glove or old inner tube, it's such an awkward shape, perhaps more so as a thumb throttle.
If I get any brilliant ideas I'll post them and any input from others would be most welcome, I fear it may not be an elegant solution.

 

[John F]

Thanks, that would be great. I'm getting a replacement this week, so if it did prove to be a water getting inside, I could take apart the old one and check it out.

 

[John F]

Would spraying wd40 or similar inside be an interim solution?

 

[Deleted member 4366]

You can fill the gap where the wires go all the way to the sensor with bath sealant, although you only need to seal from where the leads come out of the sensor to the insulated wire.

 

[John F]

Thanks. Mine also has an on/off switch which seems a weak point?

 

[D C]

I'm mainly worried about the gap where the two halves move against each other which though a very close fit is surely bound to get water seeping in.

 

[John F]

Yes that seems logical conclusion. On the other hand as they appear to work on a magnetic principle, perhaps water might not be a major issue, unless it just fills up with nowhere to go!

 

[Richard_M]

Nice post d8veh. Those halls really are as cheap as chips.

I'm mainly worried about the gap where the two halves move against each other which though a very close fit is surely bound to get water seeping in.

Hello D C, I've been filling mine with oil. I use an oilcan and pump it into the gap until it overflows. You'll find that it gradually runs out of the cable hole, but at least nothing will corrode or short inside.

As for covering it when parked up, I wrap mine with a carrier bag. A clothes peg retains it. While we're at it, disconnect all the plugs and sockets and push them into a pot of grease. Then reassemble. All the grease gets squidged through the contacts, the crimps and all over the cables.

I've had duff contacts due to corrosion but a wad of grease and plenty of oil seems to do no harm at all.
Good luck with the winter riding.

 

[John F]

I have one of those cans of spray oil with a thin spray tube. Could be just the job I guess

 

[OldBob1]

I would think packing the space where the electric wires and item with silicon grease would help.
Bob

 

[Richard_M]

Can anyone shed any light on why these halls fail ? The halls are epoxied and should be OK themselves, so that just leaves electrical or mechanical damage. I can understand the halls in the hub getting flashed if the cable gets spun and shorted or if water conducts motor drive to the halls. But what's happening to these throttles ?

@OldBob1, I'm using Morris K99 boat sterngear grease. Really thick and totally waterproof.
@John F, I'm using old engine oil. It's free and I use it all over my bikes.

Thanks again d8veh for an excellent repair guide.

Good luck with your winter rides.

 

[Deleted member 4366]

If you have a throttle with LEDs, you have 36v inclose proximity. Many are misconnected when the thin red ignition wire is connected to the throttle red. The one I just fixed was because of a short in the harness. They also fail when the hall sensor is badly soldered or when the legs break off due to vibration. Sometimes they get ripped off when the cable gets pulled.

 

[flecc]

Thanks. Mine also has an on/off switch which seems a weak point?

If it's the type of rocker switch standing proud, this section of my website may provide the answer.
.

 

[John F]

If it's the type of rocker switch standing proud, this section of my website may provide the answer.
.

It's a red push button, not a rocker type

 

[flecc]

It's a red push button, not a rocker type

Could you use the other solution, rotating the throttle on the handlebar so that the button is beneath?

 

[John F]

Could you use the other solution, rotating the throttle on the handlebar so that the button is beneath?

Could do. It would bring the cable outlet toward the top front though. I'm away from my bike right now, but I'll give all these tips a serious look. Thanks for all the tips chaps!