Hi there:
F-12 means Communication Error

First i suggest to check some bad connections, wiring faults or a bad board.

Try unplugging the dryer and checking connections, wiring and the board for burnt or bad connections.

Hope this helps; also keep in mind that your feedback is important and I'll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using Fixya, and have a nice day.