fragiletour

2013 Audi A8L

Filters have been changed but I still get a "bad smell" from the vents, specifically when the heat is on. Should I press the dealer for a solution and have others experienced the same?
It's not a burning smell or anything, just an unpleasant smell.

gk1

Hard to tell from just "unpleasant". The dealer can do a cleaning where they spray some cleaning aerosol up into the system to clean it out. I think you can buy it yourself too if you are a diy kinda guy.
Also on a few occasions I've heard of small animals cats etc. peeing on the area near the base of the windshield which would cause a bad smell for sure.

MP4.2+6.0

Make sure HVAC drains are not clogged. Dealer can check if under warranty still.

Firefighter

If your car was outside during any winter months, you may have had a rodent (mouse) try to find a home in the fan housing. I had such a problem with another car and and pouring lysol down the heater vents was the only way to get rid of it.
Just a thought.

doktorekny

Definitely hvac drains and touch it up with $20 spray that goes in each vent. It comes with a 24" clear tube. 1z Klima-clean.

A 8

Anyone know how we find the hvac drains on the D4?

rkohou

Try this it worked like a charm in 3 cars I used it in.

You can get a smaller unit as this is overkill for small spaces but that is what I use for 20 min inside the car.

LexusLSguy

This smell is related mold or mildew buildup in the evaporator. Clogged drain tubes is usually the culprit as it does not allow water to drain out. There is a cleaning product you can pump up the tubes but it's a real pain to get to.

Another home remedy that I have used in the past that works well. Take a spray bottle with 70% alchohol. Turn the fan on max sucking air from the outside. Find the spot on the front window cowl where there is the greatest suction and spray liberally. The system will have a strong alcohol smell for a few min but it will totally dicipate and leave the system very fresh. Works better then Lysol and other products. But if the drain tubes are clogged you need to fix this to prevent future buildup.

rkohou

also try this German product
Wurth A/C & Heating System Treatment 6 oz.

Wurth Air Conditioning & Heating System Treatment is a powerful weapon against accumulated mildew, moisture, bacteria and mineral deposits that emit unctuous odors. ... This easy-to-use product is equally effective on trucks, RVs, bats, and home AC and Heating systems.

MP4.2+6.0

We haven't heard from OP since December as the ideas keep churning. Maybe he succumbed to the unpleasant smell...