Re: thump noise
yeah, defrost uses the a/c compressor to dehumidify the air it puts into the cab. that's how it gets rid of the condensation built up in there. That's probably what it is, nothing to worry about.
2002 Ranger FX4
4.0L SOHC, 5R55E Auto, 4.10 8.8 Torsen, 31x10.5/15 BFG ATs