Correction: White panel Positive not Negative wire heating up

[Adventure]

I'm not sure what's causing it, the wire and controller are both heating up, bad controller or two much current? Meter shows around 17 amps I think that's what that is.

[eXodus]

more details are needed.

There are plenty of white wires in a RV.  Are you talking DC  or AC?

Post a picture when you don't how to describe it.

[Adventure]

It's DC it goes to the panel the other wires go to the battery. 

[Mlw]

Looking at the pictures it seems the wire is heavily corroded. If so there's your problem. The wire needs to be shiny copper and certainly not the color I think I see (black).

Corroded wires give high resistance so heat up as high current is passing thru the corroded wire.

Renew the wire(s) and your problem will probably be over, if not you need to dig in it deeper.

[Adventure]

Actually I stripped it recently to a shiny copper, that's a result of the overheating, the problem is I've been connecting to athe outside of the screw as you can see in the picture, ignore the bare wire sticking out it's not really connected just to demonstrate how I've had to connect it, normally the whole stripped  in tact wire would be connected. I guess I need to either fix that one connector or replace the controller.

[Mlw]

mmm, the wire gauge seems to be fine as it seems to sits snugly in the connection point so shouldn't burn.

I think you are heading the right way in saying to check the connection point first or replace the controler.