I was working on a whirlpool cabrio dryer complaint was runs for 1 min then gives the AF code. I checked the vent its a straight shot outside and there is no restriction. It is blowing the way it should so i know blower is working. So i then replaced the inlet and outlet thermistors, still nothing a min later i get another af error code. I then jumped to thinking it was a faulty pcb and still nothing. I have no idea what else would be reading air flow…
I would check for a grounded element.
This could cause it to heat on high and the board cannot regulate it so the differential temperatures would exceed spec and cause an AF.