which is positive, signal, negative in this speed controller

[jquan]

I bought the following speed controller.
https://www.l-faster.com/wp-content/uploads/2018/12/250W-350W-Wuxing-thumb-throttle-with-LCD-display-controller-kit-1-aa.jpg

The throttle has 3 wires.

blue
white
red


The model is xln21
Which wire is positive/negative/signal.

When i connect multimeter, i don't get much voltage from them.
like 0.1 or something.

 

[jquan]

I connected to another throttle, these wires might be dead.
There was no voltage for a reason.

On another throttle, i could see it working.

blue - was negative
red - was positive
white - was signal