so last night i was driving home from work, and i noticed that when i was idling, my lights would dim a little. is this normal is or this indicative of a bigger issue?

 

Alternator most likely, does the battery voltage gauge move when this happens or during driving?

 

Do you have any aftermarket audio stuff?

 

the voltmeter (or whatever it is that checks the current) IS moving down a little when i go to idle, but it goes back up if i rev the engine or start driving, so that makes me think it isnt the alternator (but i am still new to this car stuff)
i also do have an aftermarket stereo, but no subs or anything that would hog lots of power.

 

most likely the alternator. everything in the car runs off of it when the car is running, not the battery. If the power is less at idle, then your alt is most likely crapping out, and can't handle the load at the lower RPMs...

At least, it sounds good in theory.

But, it's easier to get the battery out, so try that, take it to Autozone or some place that does free tests. If it's not the battery, take the alt out and back to the store to be checked.

 

I would personally leave it be for now. A lot of cars do this and have no trouble for years. As long as it's charging.

 

^^
+1.

 

If you pull your battery make sure you know the radio unlock code, or else the radio will go into theft protection mode, and if you don't know the code (it is on a tag in the radio users manual for your specific car) Audi will hit you with a 50 to 100 dollar fee to unlock it for you. If you need to replace the battery make up some kind of a small power supply to keep the controllers in the car powered while the battery is out. Usually a 9V battery connected to a cigarette lighter jack will work.

 

actually, i already replaced the battery and did it without hooking up a power source, so it was out of power for a couple of hours, but other than the engine seeming louder, there isn't much change overall.