Air conditioner clunk

[2005 GMC SIERRA]

With the air on or off, the compressor (I guess) makes a clunk noise. It is not too loud but it is noticeable. My 2000 Chevy did the same thing. Anyone has this clunking noise? It may just be the sound the compressor makes but not very good sounding.

 

Just curious.

 

[01z71]

My '04 does it. It's really loud when I go to start the truck and the A/C is in the ON position.

 

I have never taken it in for it I just figured it was normal.

[fossil]

my 05 does also, never did it till about 15000km, its getting progressivley louder. GM says its normal but I disagree. Other vehicles dont do this

[2005 GMC SIERRA]

I think it is a GM thing. All makes will make some noise when the compressor kicks in but GM's are definately louder and more of a clunk.

[Rolandd]

Even my wife notices it in my truck

[pm26]

This is not a GM exclusive thing. My Nissan pickup A/C compressor made a loud noise every time I turned the A/C on. The clunk is caused by the A/C compressor electro-magnetic clutch engaging and metal plate clanging against metal pulley. The noise the clutch makes will vary even by individual compressor of the same make and model, depending on the clutch present gap, which is adjusted when a new compressor is assembled. For example, I replaced the A/C compressor in my Mazda with a brand new Mazda compressor and the new compressor clutch is louder than the old one was. It is possible to decrease the clutch gap by reshimming it, as long as you do not go below the recommended minimum. But, this condition is normal and you should not be worried about it.

 

What you should be worried about is constant scraping noise the compressor pulley makes even then the A/C is turned off. This most likely means that the pulley bearing is failing and coming apart and the clutch plate is cocked and rubbing on one side. Don't ask me how I know this.