I bought an electric blanket, used it for 2 months and it stopped heating up. I swapped controllers with another of the same blanket and isolated the problem to the controller. I opened it up, didn't see anything obviously burned, etc., and was not able to troubleshoot it without a schematic.
It was after the 30 day return period and the store wouldn't take it back. Contacted the maker and could not get through by email or phone.
So I bought another blanket just like it, swapped out the controller and returned the new blanket for a full refund. Such is life in the new world of Chinese-made crap.