Thanks Mike-2ptzero, when he gets home, I will check for signal. If it's getting a signal when it doesn't work, that would mean the gauge is bad? If no signal, then its where it gets the signal from that's bad?

I like how you have your tach mounted. Looks good in there. Did it take a lot of cutting to get it in there?

 

Correct and you can wire your aftermarket tach right to that cluster wire.
If you are not getting a signal then the cam sensor or crank trigger wheel sensor might be bad or maybe even the wires going to them are bad.

Mine is just mounted right to the steering column cover.

 

It's not like everyone runs 600 AWHP either When that 97 2.8 runs in the 10s, then i think the tach might be a good idea...

OP, I know you already said it's your roommate's car, and I definitely agree that to each their own. I'm not here to judge on anyone's taste, but what we have here is rarely seen on a B5 A4. Maybe it's just the AudiForum.com community, but most of us here strive to keep things as clean as possible, tastefully modding to stay looking stock, or what, in our minds, stock should have been. I can guarantee you that you are probably the only member here whose car looks like that. For most of us, we would agree that certain mods detract from the Audi community as a whole, because this is an Audi, not a Civic or Eclipse. But, like I said, I'm not here to judge. Welcome to the Forums. Stick around for a bit and you will begin to understand what I'm talking about.

But, if you already have a tach, why install another, if you can just fix the one you got

 

I checked that green wire like mike said. I wiggled it to see if that would make it work. It didn't. Turns out it was cut. It looks to me like the gauge cluster was cut out of his car before and wired back in. Gotta find the rest of wire to check it properly. Will post results.

 

There are 3 green wires, a blue, brown and blk stripe, which would it be?