ground or power side switch

starting with chapter 3 power or ground side switch decided to do test on a ford ikon in the shop purge valve koeo 12v on both wires so i think ground side switch now to find control wire unplug on first wire 12v so that is feed other wire control then it must be 0v i test and get 4v why o why it looks so easy on the videos

Computer control wires often have a bias voltage on them, this is what your seeing here
You have identified the feed and control wire correctly

The easy way to tell which side is the switch is to look at a diagram and look at which wire goes to the computer. If you see one going to ground and the other going to the computer, it's power side switched. If one is coming from a B+ source and the other is going to the computer, it's ground side switched.

I'm not sure if you can determine this with confidence without a diagram or not. I'm not knowledgeable enough to try it!

Thanks for your input I have problem with buying good wiring diagrams in RSA this vehicle is not made for other markets. There are a few such vehicles in RSA