I have a 2007 F150 xl reg cab. I'm encountering something I've never seen or heard of before so I'm hoping one (or more) of you can help me. Whenever I run my A/C my engine makes a very loud rattling sound. It only happens when the A/C is running and stops when it's turned off. Furthermore it only happens when the truck is in gear. If I'm in "park" and the A/C is running I have no problems, but as soon as I shift into either reverse or drive (but only when idling) the rattle starts. Any info or advice would be GREATLY appreciated as I am at a loss.

 

My 01 did the same thing when the bearings were going in the a/c clutch. Im not sure if yours is the same but i was able to just replace the clutch.

 

<This is my Rifle, this is my Gun. This is for Shooting, This is for Fun.>

Is that still used??? First heard it in 1949, basic training in the army in Fort Riley, Kansas. Supposedly to teach us not to call our rifle a 'gun'. Tracka96

 

Sounds like a loose nut, bolt, or connection of some kind. When you're in gear but just idleing (i.e. not going anywhere), your rpm's are going to be lower than if you were pressing the gas, or if you were in park. I'm guessing it's those lower rpm's that are causing the loose connection to rattle.

 

Im not sure, i got it from full metal jacket

 

On my brothers 06 his did the same thing. It turned out to be the mount ford used to put the motor in the truck. We took it off. Problem fixed.