Fan in my audi a3 doesn't stop running after i turn off the car. It runs for about another 10-15 min. have no idea what it can be.

 

is it the cooling fan or the A/C fan?? if its the cooling fan check all the fuses ( there are a couple in the relay box under the hood ),

it could be the fan temp sensor switch has gone down and the fan will stay on all the time even when the engine is running ( its a safety override feature ) to prevent the engine overheating