I am not sure but I think my controller is on the fritz. It allows voltage even when it is clicked to the "off" position. This does not seem right. I have written them, but no answer yet. Can someone run a voltmeter on theirs & confirm my suspicion?

How many volts are coming through? I would think it should be zero, but maybe 1 or 2 volts bleeding through is normal. Does the vest get warm when shut off?

That's all I got, mine has the trusty on/off switch... Which BTW is a PITA!

In a no load condition, it might just show a couple of volts of leakage.

You really need to check this with the vest connected via a breakout connector.

These are not simple rheostats, they pulse width modulate full voltage/current to the heating elements. Frequency is probably fixed just change the width of the pulses.

I don't have one but my understanding of it is that it doesn't change the voltage it changes the pulse of the DC...

If you have a digital VM try checking the freq and turn it up and down... the freq should change as you adjust it.

My guess is the freq will go lower as you turn it up... but I could be wrong.

Either way will work, they usually have a little LED on them.
I don't use the Widder controller but have the Gerbings one, they are not cross compatible, BTW.

On the Gerbings it does use Frequency Modulation, the little light flashes faster the more you turn it up. Usually, with that scheme, the pulse width remains constant.

I have also done the other, the frequency remains the same, flash rate, but the length of the pulse varies with the pot setting. This scheme is a little easier to implement in that the chip count is lower. But, I haven't messed with this stuff for a long time so things may have moved on.