I haven't used my A/C but three or four times since getting my 2006 in December.
Now when I'm going down the highway, or even in town, there is a loud KER-THUNK when I turn the A/C on. Anyone else had this problem? Am I about to have the compressor replaced?
Thanks!

 

my 06 does it too. sounds like it is fixing to jump out of the truck. But it happens only on the first time I turn it on from sitting. I know it cant be good on it.

 

My 05 does the same thing from time to time. Sounds like I ran over something, but I'm sitting still. But once its on and cycling, it wont make the sound again. Its a first-thing-in-the-morning thing. Almost sounds like the A/C vent door is slamming shut.

 

My 06 does it some times but so did my 01 so I don't pay much attention to it

 

Mine does it too. Scared me half to death the first time it did it. It's just normal ops for me now.

 

i actually took my '07 back to the dealer the day after i bought it, complaining of the very same thing. Talked to 2 different mechanics with Cummins certifications, seperately, they both told me all the trucks do it 1st thing in the morning, and not to worry about it.

 

i just started a thred about this 2 hours ago! sounds like a normal condition with these trucks.

 

yep my 04 is doing it. question is why?

 

Is this noise associated with the compresser? I haven't heard that one if it is, I have heard the vent doors slaming shut in the dash. I'll have to see what mine does if it ever warms up around here.

 

Yes this is normal. You may of had some liquid R134a get in the compressor due to sitting. That will cause the A/C clutch to clunk when you first turn on the A/C. I normally turn my A/C on at idle the first time for the day. I don't like to do it at speed.

 

i noticed mine is not doing it anymore now that i have been running it.

 

Mine does it and the dealer says it normal.

The problem is caused by not having a check valve for the freon.

 

I haven't even looked, but if the system doesn't have an accumulator, then that kerchunk from the compressor clutch ain't a good thing. I kind of figured it was common.
The liquid accumulating in the compressor will warp the valves. Starting a compressor up on liquid is NEVER a good thing.
I'm also starting to get a whine from under the hood when the A/C is on and the motor speed is ramping up. Probably compressor noise.

 

My 07 has been doing it since new. It also does it with the heater. I wonder if it has something to do with the blower? Anyway, I just turn the radio up louder.

 

the noize might be the flaper valve changing over for a-c. my 04 dose it and there has been complantes on this forum about them braking. threy turning the fan off then turn a-c on. if noize goes away, theres your ansuer. if its still there is the clutch on the a-c. ceep us posted.