Don't know exatly abot A2 seats, but for A6 heater element ir basicly wire and most common fault is breackage of supply wire near the heating element connection - so nothing that cant be fixed with soldering iron. Good thing - it's cheap fix, bad thing - you have to take apart whole seat to do that.
So my recommendation would be - get your DMM, check for open circuit on heater element. If it's showing open circuit - take apart the seat and check wires up to heating element, start from the element itself. If it's not open circuit, then seat should be ok, check wiring from seat connector till switch.