I’ve installed amps in vehicles all of twice, and both of those cars were not German. One was a 1997 Dodge Intrepid, and one was a 2001 Mitsubishi Eclipse Spyder. The Intrepid was fairly easy because it was huge and had a lot of open spaces, so finding a place to drill wasn’t terrible. That said, I made someone else do the drilling, as I was 18 and stupid, but not stupid enough to ruin my only car. The Eclipse was easy because the thing was a tin can and you could route wires through any of the wide open, uninsulated spaces in the whole car. I hated that car. Anyway, since the Audi is getting a whole build, I elected to start taking stuff out of the car first, to make the process (theoretically) easier. First, I yanked out the head unit, and then pulled out the seats. Well, first first, I disconnected the battery. Let’s not be ridiculous.
Audi recommends the use of an adapter of sorts when removing the seats from the car, to prevent the airbags from going off. Dr. Google seems to have the opinion that this isn’t required if you’re doing this in a space where static electricity isn’t much of an issue. I ran with that, pulled four bolts from the bottom of each seat with an allen wrench, disconnected the three wire harnesses underneath, and put the seats aside. This gave me plenty of room to work in the car. Note that there isn’t a lot of room under those seats to remove those clips, and they fasten on the top and bottom. I ended up using a flathead screwdriver to lift one clip while wiggling it out. It helps to unbolt first and then rock the seat back to get more room to work.
After that was complete, I pulled out the lower dash panel under the steering wheel. To do that, remove the cover of the fuse box, which you’ll see if you open the driver’s side door, and look on the left side of the dashboard. Those are just push clips, so it’ll pull off if you slide a flathead under and pull outward gently. There are two hex screws on the lower curve, and then one nearly dead center, that is inset somewhat, as it’s bolting in the dash cover and not the outside of the fuse box. Then, underneath the steering wheel, there are two hex screws on the bottom that need to be pulled out. The dash cover can then be pulled straight toward you from the steering wheel, and then downward. You’ll want to pull the wiring from the headlight switch and from down below, and then you can pull the whole thing out, if you want.
Once you’re done, you’re left with this:
I started with the guide on Waks Wide Web, the defacto source of garage how-to for the TT, to run the amp power cable. The guides on that site assume a RHD UK TT, so when he mentions “glove box”, it’s under the driver’s side for the US. I also ignored everything about the remote wire, since this is being controlled by an aftermarket head unit with a dedicated remote lead. I was stumped with what I saw there. First, the box that can “easily be unclipped and moved to the side” is either the thing on the left or on the right. The thing on the left provided no more visibility or ease to me when it was unclipped and moved. The thing on the right wasn’t going to budge for anyone or anything. So, I tried from the inside. He talks about the big loom, so I found that above the dead pedal, taped my 4-gauge power cable to a wire hanger, and tried to push it through.
Nope. Not going anywhere.
So, I’m shining a flashlight behind the engine. I pulled out the airbox entirely (which came in handy later), to see if I could see another hole with more room. I’m shining a flashlight all around under the driver’s side, and I’m starting to get ready to find a place to drill, or try to remove the white covering that is all along the firewall on the inside of the car, thinking maybe something is covered on my car that isn’t covered on others. Then, as usual, it was actually staring at me all along. There’s a dime to nickel size rubber grommet almost directly above the gas pedal. I pushed on it, it came out, and I could see the light from the open hood of the car. Success! I took my taped cable and ran it through that hole until it it something.
It comes out somewhere around that box that Waks Wide Web was talking about. Mine poked through the heat shield behind the engine, but I pushed it back and routed it to the right hand side. In a perfect world, this would run along the wire track that you see on the right, but as I mentioned before, I have no idea how to gain access to it. I successfully unclipped it from the bottom, but without getting to it from the top, that’s useless.
I kept the cable below the airbox, covered the cable, and put the airbox back into the car. I’m not attaching it to anything yet, but now I know my cable length, and I know where it’s going. Insert a new grommet so the metal is not rubbing against the cable, and put some sealant on there so water doesn’t get in the cabin.