Speedo freakout while pedaling with PAS

[vwhammer]

I have a S12S controller with the LCD 3 display and PAS only
While pedaling the speedometer goes crazy.
It jumps all over and goes as high as 50 mph.
As soon as I stop pedaling and coast the jumping stops and it reads the speed as it should.

Anyone have any ideas what might be causing this?

 

[amberwolf]

Sounds like somehow the PAS signal is being input to the speedo, probably along with the regular speedo signal, and it's confusing it.

Assuming the speedo is not measuring the rear wheel, then if you setup the bike so the rear wheel is off ground, and spin the cranks by hand, does the problem change?

Or, if the speedo is on the rear wheel, if you disconnect it, then spin cranks by hand, does the problem change?

 

[slowhands]

Disconnect the PAS or speedometer input from your controller. They are somehow connected, and you need only one or the other, no?

 

[vwhammer]

I believe each item serves its own separate function.

I did take not of a few things.
For starters I have the sensor on the rear wheel.
There is a motor in the rear wheel as well.
I can have the controller on for the rear motor and the assist level set to zero and the speedo will read correctly.
I can also use the front motor which has a separate controller and a throttle and the speedo reads fine.
However, the moment I set the rear motor assist level to 1 or higher and the motor starts working the speedo goes all crazy.
Must be some interference with the speed sensor signal somewhere.

I suppose I will start by routing the sensor pickup wire away from the motor power wire.

I may also move the magnet for the speed sensor out away from the center of the wheel.
It could be picking up some crazy interference from the motor itself.

I have checked and recheck connections and they all seem legit.
Anyone else have any other tips.

 

[vwhammer]

Well.
As I suspected, it was nothing more than the motor itself acting on the pickup.
I moved the pickup and magnet away from the center of the wheel and everything works as it should.
Problem solved.