Loud click, like a clutch engaging while idling
 

I've noticed that when my 3.0 is idling in park, or even sitting at a light in drive, there is a sound like a clutch engaging or something, kind of like turning on the air or something. You can hear the click and then the engine revs up a little to compensate. I can't help but think it's robbing some horse power and maybe causing some MPG loss, it happens every couple of minutes or so, I thought maybe it was the fan kicking in, but it doesn't make sense that it would be doing that all the time, anyone experience this?

Wirelessly posted (droid)

Ac compressor

I'm not using the AC though, would it do that even if the air is off?

The compressor kicks on and off regardless of whAt setting you have on the climate controls. It is very normal, but can cause a very slight power and mpg drop.

Well, if I keep the controls on vent, floor, or off, it doesn't do it. I am told when the control is on defrost of any kind, the AC compressor kicks on to act like a dehumidifier, I am going to check the mileage again now, I was averaging 15.5 miles a gallon, but I am thinking it will go up a little because I pretty much had it on defrost all the time, I'll post the results.