forum.audiv8.com Foren English Audi V8 Forum low system voltage and fast battery drain.

Hopefully there's some help here...

Audi V8q, 1993, 4.2

Battery drain is rapid- admittedly the battery could be part of the issue, so not eliminated yet.
System voltage, engine running, is about 9-10v, unless the rpms are raised, to achieve circa 12v+. then all seems well.
No charging light when the problem occurs, but the light is working.
The drain/low system voltage can result in ignition system failure.

My immediate thoughts were poor output from the alternator- I've seen something similar with my silver V8, which was alternator failure. However, the current owner has made mention of some device behind the instrument cluster, which has been an issue before, and replaced before, which is connected with this.

i'm nowhere near this car or my machine to look at this further.

Pointers please

Two things to be checked
- Fuse S30 (5A) for the instrument cluster
- at the alternator is a thin blue wire which much be on +12V while ignition is on
The blue wire is connected to the charging light. As that doesn't complain though your system voltage is below 12V, I assume that's broken.
If all that's ok then the alternator itself is the candidate.

I was convinced when I saw the car that it was a simple alternator failure, but the fella selling it kept explaining that his friend knew what it was.
Confirmed! Generator failure. Doh!

Anyway. I bought the car, the alternator has been repaired. The car is being re commissioned as we speak.
Some screen/a-pillar repairs to be done. Then it can join my fleet.

I don't know how many V8s came to the uk, but I suspect I now have a not insignificant proportion of the running ones.