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Battery wiring question

2003 Trailblazer 6 cyl. engine. I have had the luxury of other people doing my maintenance. I am going to replace the old battery and noticed this connector. Everything is fine but what is it, where should it go, and should I put it there?

Ground for the flux capacitor?

It’s hard to guess with out knowing what the other end goes to. Since you say everything is fine with it like that I would have to guess it is for something that your truck is not equipped with. (sarc) Maybe the the level sensor for the turn signal fluid reservoir? (sarc)

It looks like a ground connection for an aftermarket accessory of some sort…The factory seldom adds extra wires at the battery. They would use a terminal block away from the battery…That type of GM battery connector does not accept extra wires gracefully…A CB or other two-way radio perhaps?

Hey, nice job with the photo…

Thanks. the wire goes into the wiring harness headed towards the bottom of the car. Blinker fluid warning light sounds like the best guess so far. I was just hoping someone might have a clue, there is nothing within range of the end of the wire to connect it to, and no evidence of missing pieces.

When you find the reservoir you can get fluid here;

PvtPublic. i thought it went to the muffler bearing.

Ground wires are seldom red in color.

That’s the aux power lead for the trailer harness for providing +12 to whatever you’re trailering. It goes on the closest lug under the fuse block cover. However, you might choose to install a relay in line with it, powered off the IGN ON/RAP power so you don’t run down your battery if you forget to turn off the trailer accessories powered by it.

Thanks. On the right side of the picture is the fuse block under a plastic cover. On pulling the cover there is a 30 amp fuse marked trailer that looks to be in line with a stud that the wire in question could be bolted to if unhooked from the harness. Mystery solved and thanks, in case I ever need it!

Glad to help. I first saw that wire hanging when I was installing a plow on mine a few years back and, due to curiosity, had to figure it out. Shortly after that I discovered what a pain it is to tap into the RAP. It’s not like the old days w/ACC key position…

One thing that I still question,both the hole size and the actual diameter of the metal part of the connector look too big to attach to a 6mm stud common in the fuse box (for trailer wiring)the hole in that connector appears to be 8mm and the flat part looks much to big.

Here’s how I see it, Thanks for your thoughts.

The connector does look like a better fit in the second picture. The studs on the right are 8mm and the one you make reference too is 6mm. GM would not want you to use a wire with a connector that had a 8mm hole for a 6mm stud. Looking at it again maybe the intended connection point is that 8mm stud with the red cable on it to the right of your arrow, certainly not the ground.In the original picture the wire color looks black on my monitor

No it goes on the stud for the trailer fuse. The wire length is perfect for that stud and won’t reach the others, which I believe are unfused feeds to the block. The lug hole fits perfectly over that stud with minimal play. Lastly, that wire goes to the 7 pin trailer connector on the back of the vehicle.

Waterboy, you’ll get the best advice and information about your TB on the Trailvoy BBS. I frequent that site and there are many knowledgeable people on there with specific knowledge of the Trailblazer / Envoy.

The last thing I don’t like is the wire gague on the “mystery wire” it hardly looks heavy enough to carry 30 amps. All lighting and electric braking off this one source? seems to be taking things to the limit.

Typically I like to protect the electric brake controller I install with a resetable 20 amp breaker, not a fuse.

This is going to have to be my last post on this topic because it’s approaching the point of being ridiculous.

You couldn’t tell the color of the wire in the first photo (it looks red to me on three different computers) and you’re assessing the diameter of the lug hole and the studs (incorrectly) and now the wire gauge and whether or not it’s sufficient for the purpose (also incorrect)?

You don’t even know that the electric brake controller interface is a completely different connection on this truck. It’s up under the dash.

This wire supplies power for auxilliary devices in the trailer like interior lighting or charging a service battery for example. It has nothing whatsoever to do with electric brakes or directional lighting on the trailer. Those are completely separate circuits.

At one point you suggested the wire should go to one of the other terminals which turns out to be dangerous advice since that is not a fused point and could cause a fire if someone followed that advice and shorted out the trailer connection.

Why are you speculating so much based on so little information? Scratch that question, I won’t be back to see your answer…

It is because you said it supplied power to the 7 pin trailer harness and that is where the power for the electric brakes (if any) are supplied their power,Hows that? Take a look at a 7 pin connector, there is a tab clearly marked for electric brakes.