Redd

Sorry, this should be a general question across all Audis but there's no good section for that either.

I'm adding a battery direct electrical connection, and on the positive terminal I found a number of fusible links (one not installed) that connect with a 6mmx1.0 nut, so I'm connecting my positive lead on one of those.

But the negative terminal has no convenient connections except to the battery terminal bolt itself. Rather than loosen that, and risk the car deciding to reset itself, I'd like to simply ADD another nut to the bolt.

KISS, OK?

But I can't seem to find a simple spec for that nut/bolt size. It is bigger or coarser than the 6mm so I'm guessing, maybe 7 or 8mm default?

Wold anyone know for certain? It's a PITA to clear the spare and all, access the bolt, go to the store, screw around in their parking lot, clear the spare again...you know. Not KISS!

Surely there's a standard metric battery volt size? Which Audi might convene to?

UPDATE: As the day keeps getting better. (sigh) Well, a 7mm nut is way too big, so this must be a 6mm "odd thread" size, I thought, and proceeded to use a convenient 10mm socket to spin off the nut on there, for now.

Wrong. The square-head bolt stripped and rotated against the battery terminal clamp....argh...leaving me with a jammed nut and a not so square headed bolt that now needs to be replaced all together. I'm thinking, someone at Audi damaged the threads originally, maybe it WAS a standard 6mm x1.0 bolt that just had damaged threads. Which now will send me off for a whole new...Is it standard? Or Audi Special? european metric battery clamp nut and bolt?

USAVAGEU

I know this is probably a dumb question, but why can't you ground to the body or frame somewhere?

Redd

Radio equipment, ground loops, voltage loss, and plan old neatness all count. The positive cable has to go to the battery, so the symmetrical negative cable should go there as well.

Radio transmitters normally are connected directly to the battery terminals and fised at both sides, because of a number of esoteric issues. That's just the way it is done.

Anyway, the now useless original bolt has to be replaced, which will make it easy to "do it right". The ground cables from the battery go "somewhere down there" and I really see no need to explore that far.

Could be a 1/4x20 stove bolt tomorrow, damned if I'll let the car drive me crazy on this one.

ebi718

Old thread but still somewhat relevant. I have a similar issue....stripped squared-head bolt on the positive battery terminal (in my C6 A6). Did you get to replace that clamp alone (or the whole connector + module.)

Redd

IIRC...I bought a proper new terminal post clamp, took the stainless nut and bolt off it, and simply used them on the existing terminal post clamp, so I wouldn't have to do any rewiring. I would have just used a replacement bolt (some stores sell them) and nut made from stainless, but as usual matching up the sizes made it easier to just buy a new assembly and use the new nut and bolt.

Sometimes you can also find a "stove bolt" which is also a square-headed bolt, but usually too long for the job. Ace Hardware or TrueValue usually carry them, the big home stores...harder to find, especially if you want stainless.

So far, it hasn't generated any diagnostic error codes.(G)

It was one of those "All I want is a damned BOLT, doesn't anyone just sell BOLTS any more?" experiences, trying to find something that was the right diameter and length as well as good metal.

And in a moment of "let's do this right" I thought, I'd pick up the extra "fuse" that attaches on top of the battery. (The flat metal ones.) Nope, gotta special order that and come back to pick it up, the parts counter doesn't keep any on the shelf. I guess those fuses must REALLY drive up the cost of keeping inventory.(G)

ebi718

Thanks; I just got it (the bolt) replaced at the dealership, at no charge.

bcwhite

Did you find out the spec for this? I've had no luck finding a matching nut (for exactly the same reason). Neither M6 nor 1/4 (coarse or fine) will thread onto it. M8 and 5/16th are too large. Both positive and negative terminals are the same.