Strange electrical fault again

[green A8]

I'm not sure if I've raised this fault on this forum before I think I might have.

The car is a 2000 MY FL 4.2 QS with only just over 20K miles from new It's owner works abroad so the car is laid up for three to four months at a time. A couple of years ago the car was being readied for return to use The garage had removed the battery which was to be replaced with a new one. On connecting the new battery and starting the car the battery light glowed brightly and the new battery was quickly discharged. A new alternator was fitted the battery recharged and all was well. Fast forward two years and only three thousand miles and exactly the same thing has happened again. Is it normal for alternators to die through lack of use and at such low mileage? any ideas as to the underlying cause? No faults of any sort were found via VCDS.

[PsYcHe]

I'd be more inclined to blame the battery if it was left connected for that amount of time. If you're leaving the car for months, either fit a trickle charger, or disconnect the batter entirely.

[green A8]

Thanks for the reply.

I should have made it clearer. This time round the battery was removed from the car and placed on a trickle charger. The battery has been tested and it is not the problem. This latest fault only reared it's ugly head once the battery was re-connected. I visited the car at it's storage location this morning and can confirm that no charge is being returned to the battery. The car was last used over the Christmas period and gave no cause for concern. I would have thought that an alternator would have given some warning that it was giving up the will to live, but there you go.

As I understand it the owner is now thinking of getting shot of the A8 as he's not too amused about this second failure in such a short period of time and after so few miles. He's not prepeared to shell out another £6-700 to have a nother new alternator fitted. It would seem that he has the use of a Lexus in Dubai which has done more than ten times the mileage without ever breaking down. So, he'll probably buy a Lexus and shoot the Audi.

[ainarssems]

It might be just bad luck. Was it genuine Bosch/Valeo alternator or aftermarket or rebuilt unit, is it still under warranty? I suppose I can see that being in storage could cause corrosion buildup making bad connection for brushes or getting them stuck stopping alternator from working properly.

It's very unlike y for alternator to have terminal failure. It's normally voltage regulator that fails or brushes wear down or it gets noisy because of worn bearings.

I recently had alternator failure on our A6. New genuine alternator would have set me back £400-700 depending which one I chose as there are several Bosch and Valeo units that can be used and are interchangeable. Cheap aftermarket one would be starting at £130 but I have seen too many cheap units fail within 2 years, many even in less than year. Apart from not wanting to spend money I also did not want to take the front off the car to get belt off. Old unit was Valeo and voltage regulators are hard to find for these, one from dealer would cost £70, that's still too much, I found one on German e-bay for around £20 but before placing the order started to investigate. I took the voltage regulator off without taking alternator off, brushes were worn quite a bit and a bit sticky not moving freely also couple solder joints looked dry. Commutator looked fine, it did have some wear but probably around 50-60% life still left in it. And judging by the date stamps from year 2000 it is still original alternator done over 170k miles. So I gave it a good clean, re-soldered all the joints ant put in new set of brushes from e-bay for £3.55 http://www.ebay.co.uk/itm/1809397748...84.m1497.l2649 You can get them for £3 with economy delivery but I chose the ones with first class delivery. All fixed and working fine and hopefully will last another 150k+ miles unless bearings wear out. All for the cost of £3.55 plus 2x 1 hour of my time.

[ainarssems]

There is also video on youtube from one of the e-bay sellers http://www.youtube.com/watch?feature...&v=aVvPzwtxdrM

[Dezzy]

I've had a similar issue before with battery discharging quick, turned out to be the connection on the main cable running from the boot, on the underside of chassis leg by the drivers front wheel. It was all green powder instead of copper wire.

[green A8]

Thanks for the replies.

The alternator is a genuine Bosch 0123 520 003, 90-150A as fitted by an Audi main agent just over twenty five months ago, so out of warranty then I'm afraid.

I was informed that the car was looked at this morning by a qualified sparkey. As soon as he connected the battery and cranked the engine two things happened. The alternator gave out a cracking grinding noise, followed rapidly by a plume of acrid smoke, at this point the battery was very quickly disconnected. The only time I've ever had an Audi do a similar thing was on the M6, when the alternator freewheel pulley seized solid. The acrid smoke in that case was caused by the serpentine belt destroying itself. I'm not certain that a clutched pulley is fitted to this car, if it was then I think it's safe to say that it's kippered.

The A8 owner now intends to source and have fitted a second hand part, just to get the car running, I get the feeling that it'll then be traded in against a Lexus. I've given him the 'phone number of a certain well known A8 breaker I've also offered to beat any trade in price offered in order to save this low mileage beast, time will tell what happens. But, A8 number three could be on it's way Then again, once he drives the car perhaps he'll decide to keep it.