Inside The HWBS Sensor

I've always wondered how these brake cutoff sensors work so having another one fail I decided to take it apart.

The 2 brown rusty blocks are magnets, the end one is fixed and the inside one is supposed to be loose which I believe sticks to the cable (even the stainless cables are magnetic enough). The middle one moves up with the cable to trigger the electronic sensor, then attracted back to the end magnet to move it back down.

I've laid the parts down, in aprox the correct position length ways.

Thanks for for the pics. Having never taken one apart I'd sort of concluded they had some kind of barb/ratchet inside. This makes a bit more sense now.

 

Great post!

 

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They don't work with all stainless cables.

 

The fist time I fitted one of these I couldn't get it to work. I tried reversing it, checking the wiring and swapping it for another, which still didn't work. I didn't know it worked magnetically until I pushed a spare, non stainless, cable through and could feel the magnet gripping the cable. As I hadn't felt this on the cable on the bike I realised it must be a stainless cable and that that was the problem.

 

With a change of cable it was fine, but I do think they should come with a warning not to use them with stainless cables.

Edited November 10, 20169 yr by jhruk

This explains something I have been confused about for a long time.

 

A member on here (D C) kindly gave me a couple of HWBS's. He said they didn't work for him.

 

They worked perfectly for me, and I was at a loss as to why they didn't work for him. Now I know the answer: I'm too much of a tight wad to use stainless cables.

 

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I have one mounted since my last series of modifications. As the motor now has little to no run-on with the external PAS I don't know if I need it or not... I also find the brake icon on the LCD distracting especially at night.

Was this sensor still working before you took it apart.? Rusty as Hell the, magnets.! I have recently bought and installed these on my bike. I have also waterproofed them as much as I can.

Wrapped whole load of electrical tape around them to make em water tight.

oops sorry you did say it failed. You think because of the rust or electrics got damaged.?

Thanks

You think because of the rust or electrics got damaged.?

Thanks

I think it was from the rust as the inside magnet was seized.

This is about my 3rd sensor to fail over 3 years so was interested to find out why and am now thinking of ideas to prevent the rusting inside.

Wow that's a sensor a year. I electrical taped the wire as it was exposing the inner wires by the sensor. I also taped the the brake cable to the sensor and covered it with the rubber dust/rain cap that goes on the cable. That's was my front brake. The back brake had to be connected in a different place so I chopped the brake housing in 2 sections and electrical taped the electric wire again and the brake housing on both sides of the sensor.

I will post a picture today or tmrw for ya. Maybe save you some money on any more new senors.

Mine is vertical so water should run out the end. Sun id back out so photos are on the agenda here too.

Mine is vertical so water should run out the end. Sun id back out so photos are on the agenda here too.

That one above was vertical too...

Now I know the barrel which the moving magnets and brake cable goes through is seperate to the electronics I am considering pouring some acf50 or thick oil in and hopefully coat the magnets and the bit it slides along to protect in the future.

Heat shrink is available in larger sizes so may be that would work.

I agree even heat shrink is a good idea, maybe also a good idea to add the grease or acf50. I have added pictures of what I have done to my front brake which is vertical & my rear brake which is horizontal. Maybe I should have mounted the sensor under the downtube.

You can see where I have taped up the sensors, looks a little messy in the pictures. Actually you cant really tell looking at the bike. Never the less it protects the sensors.

I also bought a rucksack cover which I chopped up and made a bag for my controller with velcro straps also done the same for my throttle and battery for when those heavy raining days.

Will post some of the made up rain cover pictures little later.