Audi Repair Questions? Ask a Mechanic for Answers ASAP
You would have to take the vehicle back to Audi for diagnosis. If the present fault is caused by the part they fitted 11 months ago then you should get warranty on this as it is within the year (most manufacturers offer a year on Parts Warranty).
If however it is found to be something else causing the fault then you will usually be asked to pay for the diagnosis even if you didn't want them to complete the repair.
Hope this helps.
Unfortunatly you didn't mention you were 300 miles from the original dealer!
As long as you have a receipt for the work carried out any Audi Dealer can carry out a Parts Warranty claim.