Common problem...
Save your $$$ and DIY R&R the electrical portion of the switch. Parts, even locally from an Audi dealer, should run less than $40. You can order online from ************************************************************
here for $8.65.
Directions for DIY replacement here
In the mean time, either disconnect the (-) lead on your battery if car will be sitting for some time as it will drain quickly. Or keep it on a maintainer until you replace.
Dealer will most likely want to replace the whole assembly and not just the switch which can be big time $$$.
