Speed sensor issue.

[Slapbassmunky]

So, 5 miles into today's ride on my 9.8xt the speed readout starts going all over the place, with the motor cutting in/out and misbehaving as you would expect, but NO fault code. So I stopped, bashplate off, and unplugged the sensor to at least get home in limp mode.

After testing the sensor with a basic multi meter it gives several pulses per sweep of the magnet. Confirmed with a hand held scope. The reed switch is kaput. P/N W582244. By some miracle the local dealer had one in stock so all is good again. However they did say the failure rate is very high for this particular part, and it's a Trek item, not Bosch. They are a fairly long lead time, and I'll be keeping a spare with me at all times.

The local shop is working on a solution using a butchered Trek mount with a different Bosch sensor potted into place.

What are people's experiences with speed sensor failures?

 

[RustyIron]

Reed switches fail. It's a mechanical device that is expected to function for millions of operations, but they just don't last that long. I've not replaced one on an ebike, but I just looked up a very small reed switch, 0.18" diameter and 0.43" long, for under ten bucks. If I couldn't get an OEM part in a timely manner, I'd slap one of these babies in.

 

[Tortelli]

Was about to post this question on the forum when i found the tread... seems like I have the same problem with my Rail 9 with about 100km (70 miles) on the clock....:
Seems like the same problem?

 

[Slapbassmunky]

Was about to post this question on the forum when i found the tread... seems like I have the same problem with my Rail 9 with about 100km (70 miles) on the clock....:
Seems like the same problem?

Yep, exactly the same problem as mine had. It looks like your speed sensor. Unfortunately I can't upload the video of mine as it the wrong format.

 

[Yoak]

If you get speed readings all over the place the first thing to check is your magnet on the disk rotor. It’s more likely a deposit of tiny metal shavings from the rotor on the magnet, than anything else. I had this problem for a month last year on my new Rail. Took a lot of posts and head scratching to figure it out.
idismissed The problem first as I cleaned it once while still on the break disk rotor. Later I removed the magnet and carefully wiped off I’ll the little metal shavings.
that solved the problem. Typically happens when you replace a disk rotor as well

 

[Slapbassmunky]

If you get speed readings all over the place the first thing to check is your magnet on the disk rotor. It’s more likely a deposit of tiny metal shavings from the rotor on the magnet, than anything else. I had this problem for a month last year on my new Rail. Took a lot of posts and head scratching to figure it out.
idismissed The problem first as I cleaned it once while still on the break disk rotor. Later I removed the magnet and carefully wiped off I’ll the little metal shavings.
that solved the problem. Typically happens when you replace a disk rotor as well

Good advice, but my sensor was toast. I tested it with a scope off the bike with an old magnet. it would give several pulses per magnet 'sweep'.

 

[Yoak]

Good advice, but my sensor was toast. I tested it with a scope off the bike with an old magnet. it would give several pulses per magnet 'sweep'.

Yeah, I just wanted people to check the magnet first, as it’s a lot easier to do than checking the sensor I for one wouldn’t have a clue how to do that

 

[Hamina]

I think my speed sensor might be coming to it's end. LBS didn't have the Trek's own speed sensor. I wonder would it be possible to modify Bosch OEM sensor to replace Trek's own sensor. What do you think?

Trek W582244 sensor:

The 600mm Bosch sensor 1270 020 800

Bosc slim which seem to be for the BES3 M22 system I guess?

 

[L666GTB]

I think my speed sensor might be coming to it's end. LBS didn't have the Trek's own speed sensor. I wonder would it be possible to modify Bosch OEM sensor to replace Trek's own sensor. What do you think?

Trek W582244 sensor:
View attachment 79006
View attachment 79007

The 600mm Bosch sensor 1270 020 800
View attachment 79000

Bosc slim which seem to be for the BES3 M22 system I guess?
View attachment 79001
View attachment 79002

View attachment 79008

I did this with mine. Using the Bosch slimline sensor. No problems since

 

[Stihldog]

I did this with mine. Using the Bosch slimline sensor. No problems since

I’m assuming that the actuator is a simple reed-switch which is activated by the magnet on the rotor. Over time, or kms, this is likely to fail. This looks like a good option, especially for a spare, if the LBS doesn’t have one in stock.

 

[L666GTB]

Yes. The Bosch one might be a little better quality than the Trek.
I used the trek housing and bonded the Bosch slimline sensor in place.

 

[antarcher]

I had been intermittantly bothered by the bosch 503 error (speed sensor). Used to correct it with a magnet waved over the sensor or bashing the outside of frame with a log. As it will always go, the sensor totally failed after warranty during Xmas break in a remote region away from parts suppliers.

To get riding I cut the switch off and wired to the left crank with a conductive metal strip inside the crank to simulate the momentary switching needed to trick the bosch controller to think you are rolling.

Lots of hacks are posted like this but this excludes hall effect sensors or reed switches and magnets.

Am thinking of buying new trek sensor but this works and I know it won't fail again at the worst moment. Bonus is cadence is always less than wheel rotation so speed limit is overcome.

Pretty sad that the very tiny and simple reed switch by trek disables the whole NZD$9000 bike.

 

[Paulquattro]

Pretty sad that the very tiny and simple reed switch by trek disables the whole NZD$9000 bike.

To be fair Bosch make the sensors
And its not just bikes
Vehicles can be disabled by small sensors its just this tech world we live in im afraid .