VERY confusing flickering battery light

[dfux86]

Alright, this one might stump you. I noticed my battery light flickering (with no pattern or rhythm), so i scheduled w/ Audi to look at it. they said i need a new battery and wanted $250. the car starts perfectly fine and the battery level stays between the middle bar and the far right bar. but then it stopped, but now its back. but it only happens at night. now, i'm not a complete idiot, so here's the list of things that have no effect on it: headlights radio A/C raising the suspension actually driving revving the engine using any axillary item WTF? every night, after the sun goes completely down, it starts flickering on and off with no consistency. I know a warning light is generally a bad thing and i want to fix it, but what is the underlying issue?

[fjasper]

It's likely that it's just not bright enough so that the flickering shows during the day. Try cleaning the connections on both ends of the battery cables, and the wires that go to the alternator. Random flickering might be a loose or corroded connection, and the parts swappers will spend a lot of your money experimenting with it before it's fixed.

It's possible that you may actually need a battery, but you don't need a $250 Audi battery. If you decide to replace it, go to an independent shop and they'll do it for a more reasonable price, or buy one and do it yourself.

[Candor]

You probably need a new alternator. Odds are that the battery still needs to be replaced, but these alternators tend to go out slowly. You won't see a dip in the voltage of the voltmeter because it usually blows a diode or shorts across one of them. These are the only cars that do some of the stupid things that they do. About the $250.00 Audi battery, you can have an aftermarket shop install one for less, but there's about a 50/50 chance that they will lose your radio code and have no idea how to readapt the throttle plate. You'll have to limp it to the dealership and pay them anyway. If you want to be a real cheapskate and go to Wal-Mart or something, you may as well just go ahead and buy an engine control module and a new battery hold down also. $250.00 doesn't sound too bad all of a sudden. You will probably need an alternator soon, though. It's possible that it's just the battery, but unlikely that your troubles will end there. Have fun with the 4 wheel drive money pit!

[fjasper]

Particularly if cost is an issue, you either need to learn to work on this thing yourself, or find a good honest shop to maintain it for you. Or more likely, both. If your dealer has a good repair shop, that's fine, but often there's a better option.

Asking for a recommendation in the forums can be a start, or you can look in the yellow pages for auto repair places that specialize in VW/Porsche/Audi. Find out if there's a VW/Audi club in your area and see who they recommend.

It's not really worth much to have the dealer enter the radio code, since the directions are in the radio manual. Throttle plate adaptation is also easy. If you think ahead about this stuff, a set of jumper cables can make it so you don't have to do either one.

If you're going to work on it yourself, you may want to get a Bentley (shop manual) and a VCDS/Vag-Com (computer interface) if you don't have one yet. Part of the basic toolkit required to work on these cars.

Don't get scared, it's just a car, but there are right ways to do things that your average mechanic isn't going to learn about by working on American or Japanese cars. You don't want the mechanic to get his training by trial and error on your car.

$250 for a battery seems like an unnecessarily expensive first step, particularly if it's the alternator that's the problem, which is likely. Check into having a reputable local shop rebuild your existing alternator. Sometimes it's a cheaper alternative, and you know you're getting a real OEM part back.

I still recommend starting with the cheap stuff and working your way up instead of parts-swapping until it goes away.

<Rant>
Don't take this the wrong way, but if you can't afford to (or don't want to) maintain this car, you should get rid of it. Cheap to buy, expensive to maintain, especially if a previous owner skimped on maintenance. It has expensive systems that will eventually fail, and they'll fail sooner if you can't afford to maintain them on a regular basis. Driving with failed air springs will do more damage. Skipping the timing belt service can require repairs that cost more than the car is worth. Ditto for using cheap oil. It has a high-strung motor in a complicated car with an advanced suspension, and even if you got it cheap off the used lot, it's still just as expensive to maintain as it was when it sold for $50,000 or whatever it was.
</Rant>

Ok, I'm over it now.