What is this wire?

[4angels]

See picture, red wire on upper left has a flat round mount that looks like it is supposed to be on the open stud on the fuse box. Also, there is a little corrosion on the mount hole so clearly it was connected somewhere before....

Only thing that doesn't work right is the dome/entry lights don't come one when I open the door. but they come on when you manually turn them on?

SO, any ideas?

[06MidnightBlue]

I'm interested to know this too, as I have something similar to that on mine. Looks like it should tap into the battery but it's unplugged and has been that way since I bought it.

[The Roadie]

This is one of the top ten questions that noobs to trailvoy and gmtnation ask. Actually, it generates about one or two new members every week! For years.

Anyway, if you attach the ring lug on the mystery red wire to the adjacent threaded stud and install an M6 nut, it powers up a pin in the rear 7-pin trailer connector that recharges trailer batteries while you drive along. Many folks think it's involved with the electric trailer brake harness, but it's not. It's forever unknown WHY the GM designers left the ring lug off the stud, but there are a couple of theories.

Anyway, the stud (and my M6 wingnut) is shown in this picture that's been posted a hundred times on the various sites (including here, I think). Mostly it explains how goofballs blow their megafuse in a jump starting exercise gone horribly wrong.

[4angels]

Thanks for the answer Roadie. Of my 3 TB's over the years this is the first one that had that disconnected.

[Karo]

@The Roadie
Nice Megafuse mod, but why did you go 25Amps stronger?
Reminds me to check if i have all spares together..

[Trail X]

The 150 is much more readily available here.

I feel it also adds a certain level of added safety margin against blowing the fuse when it's replaced. If it blew solely due to high pull and not a short somewhere, it might allow you to proceed with your journey with the added 25 amp capacity.

At least that's my thoughts, I too have a 150.

[The Roadie]

What JD said. I also measured the current through the wiring to the rear fuse block, since I connect my fridge battery there, and a totally flat discharged battery only draws 70A due to the limiting resistance of the wire from the front to the back. One of my most useful tools is a clamp-on ammeter using a Hall Effect sensor that can measure DC current on a wire without disconnecting it. Good for alternator troubleshooting as well as those very subtle 10mA parasitics.

When I bought my fuse, they weren't stocked in any of the local parts stores, but I was determined to not pay $18 at the dealer. So I located mine in the DC power distribution section of a marine store. LOTS of great and inventive expedition-quality gadgets in marine stores.

Now they're everywhere. You kids have it easy.