I have a couple of wiring questions for any experts. My truck does not have the camper special pkg, but has two batteries. It looks like it was done later. Anyways here are a couple of pics of questionable areas. Kust run slide show for a close up. Still new on publishing pix.

Truck

Curious as to what the plug is for, and notice a couple of jumpered wires on the left.

On the firewall, it looks like part of the dual battery setup, but just below is a wire inside what looks like original harness.

I also have a tiny on/off switch at the bottom of the dash between the steering column and the radio.??????????

Any clues??

 

The harness under the dash is for an aftermarket alarm or keyless module.
Wouldn't know whats under the hood without following the wires