There is a very noticeable thud when the A/C compressor engages. Or possibly the cooling fan engaging? It only does it when the climate controls are in the defrost or A/C mode at low vehicle speed. It has done it pretty much as long as I have owned it, but seems to be more noticeable lately. Does the cooling fan engage in low ambient temps? Is this normal? Is there a fix or just live with it until something breaks?

 

Mine does it too, seems to be worse when its cold out.

If I wait a few minutes after the enigne was started its not noticable, nor if the a/c is on when I start the truck.

 

My 1998 12v did it, so did my 2003 HO and my 2007 does it. None ever dropped the AC. Mine all sounded so bad the truck would shake when the noise happened. am used to it now and ignore it. FWIW - I logged mine as a complaint with the dealer for each truck in case the compressor went south. OK so far.

 

My 06 also, after sitting first use is ratchet sound followed by bang then no more until it sits a while. Coldest air of my other vehicles.

 

My 06 has recently started doing this. Sometimes you can actuall feel the "THUD" in the floorboards. I was talking to my FIL who is a Ford wrench and he thinks it could be the A/C clutches going south. I am going to have it checked out in the next couple weeks to get another opinion. I will keep you all updated.

 

Normal.... has to do with the location of the a/c compressor and the accumulation of a/c oil. Initial engagement makes the noise.

 

mine has done it since the day i rolled it off the lot.

 

Mine use to do the same thing until I was reading a post on here about the AC "thud" when it was turned on and it was talking about checking the nut on the front of the compressor to make sure it was tight. I checked mine that evening after work and I was able to tighten it about 1/2 a turn. No more thud since then and that was almost a year ago. Just something you might want to check. Here is the link to the thread below.

https://www.dieseltruckresource.com/...d.php?t=266802