Hi,

The interior items are fed current directly from the battery positive post by a separate smaller wire.
There could be corrosion or frayed ends under the terminals. Mostly off the big cable end.
That wire goes over to a little black box on the fender well.
Just because it looks small doesn’t mean it can’t be a bigger thing.


When you have a voltage reading across the battery you only get the battery voltage.
Your problem lies down the line. This can happen on either side of a circuit or circuits in this case the head of the snake can mostly like be a battery connection to the terminal block or the tabs there and any associated wiring.

I already told you about the big cables.
If you are having so many different problems you need to start from the supply side and work outward.
The next place is the fuse panel in the front door hinge area.
A problematic area due to its a cold place that draws moisture to it.

It doesn’t help that the fuse holders lose tension either and combined with corrosion on the tips it become a one by one chase unless you clean them all. I keep some very light spray every couple of years on mine but the I keep my cars inside a lot or living in California helps with less humidity.

If you are lucky in some respects, that the problem are where I suggested it be, then you have a fix at HAND 🤭 and some light work.

Phil