Repairing Audi 100 Bose Audio

Audi provided a Bose stereo as an option on the Type 44 100, 200, and V8, among other models. Unfortunately, as they get old the Bose units tend to fail, and replacement is difficult due to the proprietary nature of the system. Repairs can also be very expensive, but there are some low-cost (or free) solutions.

The Bose system uses four 1-ohm speakers, each with its own built-in amplifier. Four lines go to each speaker enclosure, apparently two for power, one for ground, and one for signal (but I'm not sure on that).

One thing that's sometimes a problem is a lack of audio output or crackling from the rear speakers. After checking the obvious (fader control on the head unit), you can narrow it down to an individual speaker by plugging the Bose unit into the other side's plug. If you then get audio, the problem is not in the speaker (check wiring or the head unit).

Fixing the rear speakers can be free. In the summer of 2002, Audi of America recalled all 1990-1991 100s, 200s, and V8s with the optional Bose stereo. Supposedly the rear amplifiers had faulty capacitors that could leak electrolyte and start a fire (several Type 44s were destroyed this way). If your car has not had the recall service done yet, take your Audi to the dealer and they will replace both amplifer units free of charge. You will then have a working sound system at no cost.

The front speakers, however, are not covered by this recall. If your problem lies in the front speakers or if your rear speakers have already had the recall service performed, it will cost money to fix but it still might be cheap.

If your problem is with a front speaker, first disassemble the door panel. You might be helped by my window regulator repair guide in getting the door apart.

Once the door is disassembled, remove the Bose unit by unscrewing the four Phillips screws holding it in. Try not to lose the three plastic spacers behind the enclosure, or the four washers in front. If the screws are rusted, now is a good time to replace them (I put in stainless steel replacement screws).

To avoid opening the other door, if one front speaker doesn't work, you can verify that the speaker is the problem by plugging it into a rear speaker connector, both of which are easily accessible in the trunk.

Once you have confirmed it is in the Bose speaker unit, open the speaker enclosure. There will be a number of 1/4" hex screws to remove, as well as a few more screws inside holding the amplifier board into the enclosure. Visually inspect the amplifier board. If anything looks burnt, you have probably found your problem.

If the amplifier board visually looks good, the problem is most likely in one of the passive components on the amplifier board. Over time, the electrolytic capacitors have a tendency to break down. In our 10+ year old cars, it is not uncommon to have bad electrolytic capacitors. If you are good at soldering, you can fix this yourself; otherwise, find somebody who you can trust to solder a several-hundred-dollar-value circuit board. Desolder all the electrolytic capacitors, noting which value was where (taking a digital photo beforehand is recommended). Purchase replacement capacitors, making sure you can match the capacitance exactly (analog electronics tend to be picky) and have at least as high of a voltage rating as the old capacitor. Solder the new capacitors back on. It is very likely that your problems are now solved. If the amplifier still does not work, I recommend contacting a Bose repair place, such as:

Last updated 2003-11-21
Eric Rechlin
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