i have an 02 3.0 A6 avant with a heat problem. when i'm driving the heat works no problem, but when the car is idling cold air starts coming out the vents. sometimes this happens very quickly, like while at a stop light. any ideas?

Might be a blower or vacuum problem. Do a search to see if others have had the problem and determine what they did.

Check your coolant level. Mine was doing the exact same thing. Added coolant, problem gone.

did a search and didn't really find anything. coolant level seems fine. the engine temp seems fine (at least the gauge isn't moving). while under way, the heat works great, but starts blowing cold air as soon as the car idles. anyone else have this problem?

My coolant level was right near the low line when this was happening. It seemed fine to me also.

The other thing it could be is a heater core going bad. Or a thermostat.