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Audi A4 Battery Change

Hey everyone,

I was trying to change the battery in my 2002 Audi A4 1.8T. Everything was going great until I noticed an extra small wire in a plastic casing attached to the positive side of the battery but separate from the terminal connector. The wire seems to run over to the top of the driver’s side of the engine. Any ideas as to what this is and how to deal with it when changing the battery? Thanks for the help!


You don’t seem to be getting much action on your question. I suggest an Audi specialist board. Within the last few weeks I was looking at a battery catalog in an aftermarket automotive dept in a big store. There was a section that dealt with an extra wire and what to do with it when installing an aftermarket battery. It may or may not have been for Audi. I don’t remember what the wire is for. It could be for a battery temp sensor to better control charging. You better be prepared to sacrifice some Audi feature if you are not going to install one of their batteries.

I’ve been trying to find an online catalog with pictures but no luck. Positive cables often have two leads coming off the battery, one going to the alternator and starter and another going to a junction point in a fuse box. I don’t know this car, but look for the engine compartment fuse box somewhere in or on the plenum just below the windshield.

Did you buy it new? If not could it be some after market add on, maybe a radio or amp? I have a 2002 VW A4 and I don’t recall such a thing, but I do have a diesel and I am too comfortable to run out to the garage right now and check to see if I have a like wire.

Hi Dave, the answer to your question may be found here: