Mine never worked from the get go... I bought my Ford 500 2005 in 2009. The dealer (go toyota arapahoe Centennial CO -- real cheats - don't buy anything from them) also sold my wife a 3-year warranty for $2400 and they never fixed anything. They routhlessly discouraged my wife of taking the car to their repair shop for issues that needed attentions. Bad, bad, bad Go Toyota Arapahoe.
Anyways the seats warmers never worked. we just put a blanket on the seats during the winters. You do the same and save $600.