New to me 1983 wagoneer limited

[tgreese]

Looking at the wiring diagram, the defrost grid connects to power and to ground. I recall the ground in the tailgate is a stud or screw; there is a legend for the type of fastener (stud or screw, thread size) on the diagram.

There is also a 'heavy duty' trailer connection accessory that takes power from the tailgate feed to run its relays. Might check that out too.

If you don't have the paper copy of the manual for '83 (the TSM, not the Haynes/Chiltons book), suggest you look at diagrams available for close years and trace out what you have. The paper book comes with full fold-out diagrams with the whole diagram on a single sheet.