Advice please. E8000 speed going haywire & motor cutting out but cadence steady

[KLONG]

Hi guys.
Please can the hivemind help.
My E-Sommet VRS E8000 has developed an issue. No fault code comes up though.
When riding the speedo on the display keeps jumping up to 2 or 3 times the correct speed for couple of secs, which corresponds to the motor disconnecting. Presumably it thinks its going over the restriction.
Magnet is correctly aligned and I've visually checked the speed sensor and connection into the motor. Also the cadence on the display does not jump about like the speed does & always shows the correct RPM.
If its just a faulty speed sensor I'll prob just replace it rather than deal with CRC warranty dept again - 10 weeks to get a replacement for an obviously faulty battery! But as the cadence is correct I'm unsure.
Thanks

 

[Zimmerframe]

When riding the speedo on the display keeps jumping up to 2 or 3 times the correct speed for couple of secs,

You're not riding off cliff's or anything ???

OK, so whilst you've visually checked the speed sensor and the connection, I'd be temped to unplug the connector at the motor, make sure it's clean and re-seat it . Sommet's can get a lot of crap in around the motor area.

I'd also check the cable routing carefully which is the most likely problem. If the suspension movement is either trapping or stretching the cable at all it can cause false readings. It might be the cable is already damaged from being stretched/trapped , so whatever you do the problem could persist. However, the Shimano cables generally seem quite good at magically sorting themselves out once you have them routed with no pressure on them.

 

[KLONG]

? No cliffs yet but the descent between Pen-y-fan & Pen-y-big was a bit like surfing a rock slide!

Thanks for the tips. I had checked the connection into the motor properly & that was fine but haven't checked the cable all the way through yet as it does seem to pass under the shock pivot. Its quite a tangle in there eh! Seems to be no way to do that without some involved disassembly.

I'm confused as to why the cadence would be fine but speed is jumping.
I would have thought the speed sensor just reads the RPM (cadence) as the magnet passes on each revolution and the speed is calculated from that based on wheel circumference?

 

[Zimmerframe]

The cadence is calculated from the crank speed (pedal turning speed), where as the "speed" is calculated based on the wheel size and the wheel sensor picking up wheel revolutions.

Can't remember if there are any threads on getting at the cable areas and cable routing .. it risks being chatted up, but @Gary might know.

 

[KLONG]

That explains it perfectly. Nice one thanks ?.
It's about time I got the tools out and worked out how it comes apart/goes together again anyway.
Have a good weekend. Think I'll be taking the Capra out to the local woods tomorrow instead.

 

[Gary]

getting at the cable areas and cable routing .. it risks being chatted up, but @Gary might kno

Cable routing on the Sommet is pretty simple. Even more so if you drop the motor. But first check the magnet is correctly positioned on the wheel and the sensor is picking it up. (bike in stand or flipped upside down)
Next check your connections in the connector bay. (3 crosshead screws and the plastic case comes off). Water/mud has an easy entry in the back of here on the vitus as there's a gap between the motor and the lower shock mount/cable nest. Hosing/jet washing the shock/down tube actually forces shit in there.
Clean everything up (dry) and test.
Then plug the poorly sealed entry AND seal the plastic case. (tape or silicone (or both)

 

[KLONG]

Nice one. Thanks for the advice Gary.
That'll be my next project

 

[KLONG]

Speed sensor cable was pinched under the main pivot (which I had to drop out), just as you described @Zimmerframe.
Swapped it out for a new one and it's all reading correctly .
Also noticed cable rub on the pivot so have cable tied everything clear. Looks like the original builder rushed the job, hence the pinch & rub.
Now to seal up / cover the gaps. As Gary said it was full of crap.
Thanks again for the info & pointers.