Has anyone else experienced their a/c blower speeding up and slowing down? It doesn't seem to matter if the system is in auto or Manuel? I've had the truck back to the dealership 3 times for this problem and they're saying it is a normal function? I had a 2012 F-150, FX4 which didn't do this, the 2014 F-150 FX4 I have now, didn't do this when it was first purchased! Anyone have any ideas?

 

I have a 2014 5.0 when you let off the gas the fan feels more powerful. Haven't had it checked out.