under 1000rpm when A/C is on im getting a rattleing/ticking sound and the idel is a little rough. over 1000rpm sound goes away and roughness goes away. with A/C off it runs great. anyone have any ideas what problem could be?

 

Yeah... I have this too.

Seems to be the compressor. Can you also feel a vibration in the brake pedal when stopped at a light? Thats what annoys me lol

 

New owner of a 2008 F150 and mine does the same. Annoying, but glad to know it happens to everyone .

 

They are made that way. When they kick on and off they tick as the compressor comes on. Nothing to worry about

 

...but when you hear a loud screeching followed by smoke from the cowl, then a "pop" noise- that's bad. Your compressor shaft and pully just siezed and snapped off. That will only happen when your a mile down a muddy trail in the woods on a Sunday though.