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1999 Audi A4 1.8T w/Concert headunit

The real reason for this article is to help people out with the wiring diagram for the harness in the 1999 Audi A4s. That is the primary piece of info that would have helped me out online. Otherwise, the info here is pretty standard and this is NOT a super hi-fi set-up experience. This is a "I want the harness wiring diagrams to fix/replace my rear amp" experience. Hopefully this article makes you feel more comfortable about attempting this.

I purchased a pre-owned A4 sigh-unseen for a great price that came delivered with a missing rear-amp (and turbo clamp and ac belt, I quickly discovered! :) ). Although the dealer offered to get me one as soon as another A4 came through his lot, I opted to just install a third party amp rather than wait (after waiting 4 weeks first) and to avoid the fact that if the dealer pulled it from another A4, then someone else would have to deal with it. That just didnt seem right to me. And since the dealer was apparently dumping this otherwise good Audi for such a good price for the reasons explained above, I couldnt complain about this very simple and inexpensive fixes. However, the rear-amp fix, if I used an Audi part (8d5035401), which came as both speaker and amp only, would cost about $200 with no dealer mark-up. Since it was such a dinky amp (the base Concert speaker set-up), I figured a 200w 2-channel amp from anywhere would actually be better. I got one for $50 from Walmart, no less, to fit the bill.

The rear amp is a smallish thing, normally attached to the rear left speaker (sedan) in the rear deck plate. It appeared to me the amp had somehow been broken off the speaker as parts of the molding on the lower portion of the speaker were broken. The harness that comes from the head unit was just dangling. I searched for wiring diagrams for the harness but no luck, so I got out my trusty multi-meter, a small pc-speaker with stripped wires, and went to work. Here is the wiring diagram:

The brackets represent the slots that slid into the male harness end. The side with the outward piece is the piece I chose as the "top".

________[ ]________
(1) (2)
(3)
(4) (5)
(6)
(7) (8)
________[ ]________

1: White- Switch
2: Red-Blue lead to Right speaker
3: Brown-Red lead Right speaker
4: Red-Blue (thicker): 12v
5: Blue-Green Right pre-amp from head unit. I am assuming they are pre-amps as I got a voltage reading of about 1v with the volume full blast. It was just enough to just barely run the speakers or the pc-speaker at full blast as well.
6: Red-Green Left pre-amp from head unit
7: Brown (thicker) Ground
8: 2 Brown-black Grounds for pre-amp leads.

You should probably check this out on your harness if you are replacing your stock amp (and/or speakers) to make sure. You know the disclaimer routine.

As you can see, there are no left speaker leads. My understanding is the amp/speaker setup comes with the amp having a direct connection to the left speaker terminals.

First I cut off the harness, stripped wires, and loose-wired all the wires to my new amp before mounting. Once I was satisfied again that everything was what it appeared, I proceeded to mount the amp with four galvanized zip screws to the rear deck from below. I made sure to attach it to double walled areas with nothing above it so they wouldnt come through the deck. I also removed the rear deck cover to facilitate in running wires, but it really didnt help that much anyway. I mounted the amp close to the left speaker as I had already mounted a 6-CD changer to the rear deck near the right speaker. I was able to put the amp quite a ways back and out of the way. Because the amp was so cheap (but still well overmatched for the crap base speakers Audi put in) and light that I am sure the 4 zips would hold it there fine forever. If you are doing this with a real amp that is heavier, I might suggest actually bolting the amp to the rear deck. Then I proceeded to really wire. Since my amp had rca jacks in, I had to cut up an RCA cable, strip wire that to the pre-amp leads. All the pre-amps and leads I finger wired together, folded over, and wrapped with electricians tape, then wrapped again with a layer of gaffers tape. The power and the switch I used orange (small) wing-nuts and then wrapped with electricians tape. I did not use the #7 Ground/Common and grounded the amp directly to the rear deck. I dont think it matters to not use the harness ground, and perhaps I should have tested that... If anyone has a good reason you should, please let me know as I would be happy to know that if it helped anything out.

For amp-to-right speaker connection, I actually pulled into the wire run that came into the harness where it passed by the amp and ran it directly the amp rather than piggy-tail it from the harness point. For the left speaker, since I had the rear deck cover off, I measured my needed speaker wire length, cut it, then took out the speaker and soldered the wire length directly to the terminals. Then I reinstalled the speaker and ran the wire to the amp. This only required about an 10 inch length of speaker wire.

I tested everything, turned the gain almost all the way down on the amp (this seemed to match the front speakers best). Left it on flat (full range) for crossover (that seemed to be best as well), and left the bass-boost (loudness) on. I put everything back together and tested again. Great! The stock sound system in the A4 pretty much sucks, and this new amp pretty much didnt change a thing to that status I am sure (I have test driven other A4s with same sound system and they sound pretty much the same, sucky). But at least the rear speakers were working again. It made me really appreciate my "Sun & Sound" package Infiniti sound system in my 2003 Mitsubishi Eclipse! Wow, what a difference. But I would say that the A4 sounded about the same as my 2000 Honda Accord EX with the JBL speakers and stock head unit (again, nothing to rave about, but fine for just plain old drive along music/news).

One thing I noted: The right speaker was marked 4ohm. My amp was 8ohm or 4ohm bridged. Since my amp was cheap, but surely had much more wattage (even if we assume the real wattage of this 200w amp is only 40-60w/channel sustained that had to be more than the miniscule little amp that is installed on the stock system), hooking up small 4ohm speakers to an 8ohm amp meant that the speakers would draw more than it should, but so what. I think it will handle it.

I couldnt find complete instructions on how to replace my brake pads and rotors, so I decided to go ahead and make my own.

These instructions are for replacing the stock front brakes and rotors for a 1999 Audi A4 (the old style, not the 99.5 body) with ATE Powerdisc slotted rotors and Mintex Red Box pads (without the sensor). Im assuming that you already know the proper procedure for jacking up your car, and for removing the wheels.

This took me about 2 hours for the first wheel, and 45 minutes for the second wheel (after I figured out what I was doing).

And of course a disclaimer: Do no attempt this if you are uncomfortable with servicing your vehicle, are not mechanically inclined, or are afraid of getting dirty. The following is only an illustrative guide and is not a complete set of instructions for brake servicing. I make no warranty on the accuracy of this information and am not liable for any damage, injury, or death that may occur as a result of using this information.

Getting Started Tools needed for replacing the brakes: Torque wrench (that measures in the 80-110lbs range) 7mm hex tool 17mm socket A light
	Remove the wheel. Identify the following pieces: Brake Caliper: This is the bulk of the item that is clamped onto the rotor, and is what youll be removing. The yellow-colored screw socket in the photo is part of the brake caliper. Caliper Bracket: This is the piece that secures the brake caliper to the axle. It is the bright green component in the photo. Spring Clip: This is the metal wire clip that secures the outside of the brake caliper to the caliper bracket. It is the red piece in the photo.
Remove the Spring Clip
	Using a pair of pliers, pull the spring clip out of the caliper. You should grab the clip at the section where it enters the hole in the caliper, and pull out away towards the back of the car.
Remove the Brake Caliper
	Locate the two 7mm hex screw sockets in the back of the brake caliper (they are the yellow parts in the photos, and are made of rubber). Each has a plastic cap on it that has to be removed by prying it off with a flathead screwdriver. Unscrew the two hex screws. Remove the brake caliper from the caliper bracket. If the caliper seems to be stuck on there, try grabbing the caliper and pulling it towards you, with a little force. That should retract the piston enough to loosen its grip on the rotor and allow you to remove the caliper. Have some kind of platform ready to rest the caliper on. This allows you to get the caliper out of the way without disconnecting the brake line (which Im assuming would make things quite messy).
Retract the Brake Piston
	Remove the outer brake pad but keep the inner one on, for now. Youll probably need to pry it off since the Audi pads seem to have a sticky film that glues the pad to the caliper. Because your new pads will be much thicker than the old pads, youll need to push the piston back into the caliper to be able to fit the new pads onto the rotor. Check your brake fluid level and unscrew the cap, if necessary. Pushing the piston back will raise the fluid level so you want to keep an eye on it and make sure you catch any overflow. I used a C-clamp to push it back, which seemed like the easiest way to do it. Remove the inner pad.
Remove the Caliper Bracket & Rotor
	Remove the two 17mm bolts that fasten the caliper bracket to the axle (the two yellow lines show where the bracket is attached). The bolts are extremely tight, and can be very difficult to loosen — especially if youre only using triangle stands because you have very little room for leverage. I had to use my foot, and also my jack to apply enough force to the socket wrench. Remove the caliper bracket. Once the bracket is removed, remove the rotor (if it hasnt fallen off already).
Installing the New Pads and Rotors
	Now do everything in reverse for the new components. Because I replaced both the pads and rotors at the same time, I didnt have to worry about re-bedding the existing rotors. However, Ive heard that the Mintex are exact OEM replacements so re-bedding may not be necessary for you if you just replaced the stock pads. Install the new rotor. Attach the caliper bracket with the two 17mm bolts. You must tighten them to 92 ft-lbs. Insert the new brake pads into the brake caliper. The brake pad with the metal flanges is the inner pad that attaches directly to the piston. Attach the caliper to the bracket, and fasten with the two 7mm hex screws. Cap the screw sockets with the two plastic caps. Insert the spring clip back into the caliper. Putting it back in is harder than getting it out. Make sure that its completely seated. Put your wheel back on. Repeat steps 1 through 22 for the other wheel. Check your brake fluid level, and bleed them if its over the “max” level. Replace the cap. Test drive your car around the block slowly. The Mintex pads recommend light braking for the first 200 miles to allow them to bed properly. Update: After putting about 400 miles on them, the pads and rotors feel fine, although the pads certainly lack that "bite" that the stock pads have. Yes, brake dust is cut down, but personally I like the stock pad "bite" better.

I couldnt find complete instructions on how to replace my brake pads and rotors, so I decided to go ahead and make my own.

These instructions are for replacing the stock front brakes and rotors for a 1999 Audi A4 (the old style, not the 99.5 body) with ATE Powerdisc slotted rotors and Mintex Red Box pads (without the sensor). Im assuming that you already know the proper procedure for jacking up your car, and for removing the wheels.

This took me about 2 hours for the first wheel, and 45 minutes for the second wheel (after I figured out what I was doing).

And of course a disclaimer: Do no attempt this if you are uncomfortable with servicing your vehicle, are not mechanically inclined, or are afraid of getting dirty. The following is only an illustrative guide and is not a complete set of instructions for brake servicing. I make no warranty on the accuracy of this information and am not liable for any damage, injury, or death that may occur as a result of using this information.

Getting Started Tools needed for replacing the brakes: Torque wrench (that measures in the 80-110lbs range) 7mm hex tool 17mm socket A light
	Remove the wheel. Identify the following pieces: Brake Caliper: This is the bulk of the item that is clamped onto the rotor, and is what youll be removing. The yellow-colored screw socket in the photo is part of the brake caliper. Caliper Bracket: This is the piece that secures the brake caliper to the axle. It is the bright green component in the photo. Spring Clip: This is the metal wire clip that secures the outside of the brake caliper to the caliper bracket. It is the red piece in the photo.
Remove the Spring Clip
	Using a pair of pliers, pull the spring clip out of the caliper. You should grab the clip at the section where it enters the hole in the caliper, and pull out away towards the back of the car.
Remove the Brake Caliper
	Locate the two 7mm hex screw sockets in the back of the brake caliper (they are the yellow parts in the photos, and are made of rubber). Each has a plastic cap on it that has to be removed by prying it off with a flathead screwdriver. Unscrew the two hex screws. Remove the brake caliper from the caliper bracket. If the caliper seems to be stuck on there, try grabbing the caliper and pulling it towards you, with a little force. That should retract the piston enough to loosen its grip on the rotor and allow you to remove the caliper. Have some kind of platform ready to rest the caliper on. This allows you to get the caliper out of the way without disconnecting the brake line (which Im assuming would make things quite messy).
Retract the Brake Piston
	Remove the outer brake pad but keep the inner one on, for now. Youll probably need to pry it off since the Audi pads seem to have a sticky film that glues the pad to the caliper. Because your new pads will be much thicker than the old pads, youll need to push the piston back into the caliper to be able to fit the new pads onto the rotor. Check your brake fluid level and unscrew the cap, if necessary. Pushing the piston back will raise the fluid level so you want to keep an eye on it and make sure you catch any overflow. I used a C-clamp to push it back, which seemed like the easiest way to do it. Remove the inner pad.
Remove the Caliper Bracket & Rotor
	Remove the two 17mm bolts that fasten the caliper bracket to the axle (the two yellow lines show where the bracket is attached). The bolts are extremely tight, and can be very difficult to loosen — especially if youre only using triangle stands because you have very little room for leverage. I had to use my foot, and also my jack to apply enough force to the socket wrench. Remove the caliper bracket. Once the bracket is removed, remove the rotor (if it hasnt fallen off already).
Installing the New Pads and Rotors
	Now do everything in reverse for the new components. Because I replaced both the pads and rotors at the same time, I didnt have to worry about re-bedding the existing rotors. However, Ive heard that the Mintex are exact OEM replacements so re-bedding may not be necessary for you if you just replaced the stock pads. Install the new rotor. Attach the caliper bracket with the two 17mm bolts. You must tighten them to 92 ft-lbs. Insert the new brake pads into the brake caliper. The brake pad with the metal flanges is the inner pad that attaches directly to the piston. Attach the caliper to the bracket, and fasten with the two 7mm hex screws. Cap the screw sockets with the two plastic caps. Insert the spring clip back into the caliper. Putting it back in is harder than getting it out. Make sure that its completely seated. Put your wheel back on. Repeat steps 1 through 22 for the other wheel. Check your brake fluid level, and bleed them if its over the “max” level. Replace the cap. Test drive your car around the block slowly. The Mintex pads recommend light braking for the first 200 miles to allow them to bed properly. Update: After putting about 400 miles on them, the pads and rotors feel fine, although the pads certainly lack that "bite" that the stock pads have. Yes, brake dust is cut down, but personally I like the stock pad "bite" better.