Hi, I've got a 98 Audi A6 -- VIN B (8th digit) which is the later model 98.

Supposedly there are TWO heater fans... a main one and a booster. The one I need is in the passenger side footwell dash.

Would this be the main or the booster... any ideas?

Thanks!!!

 

I would assume the main one is the one that has direct correspondence/access with/to the HVAC Box. If your Heater box (I would assume it is) is directly off center over the passenger side footwell, then you have your answer.
I would also assume that you have dual climate controls, so the "booster" blower probably services the driver side.
These are just assumptions though, as I don't have in my old and crappy 95 dual climate.

 

There is only one fan. There are several motors, but these are vacuum motors for controlling various flaps. Not sure where you are getting your advice from, but I looked this up in the parts manual (Google A6C5partslist).

Bob