SV6 vibration/buzz

[VPFreak]

Hi all, this one has me stumped. Ever since I have owned this car for 5 months it has a slight vibration or buzz sound on light throttle at around 1300-1400 rpm and only when in drive. Now I have noticed that if you turn the AC on it goes away. If you put it in drive and increase revs to 1300 you can hear it and as soon as you turn on the AC it goes away. It does not do it in park or neutral at the same revs. I have checked all the AC pipes as I thought it they could be vibrating against something however everything is tight and free from rubbing on something else.
I originally thought it was one of the heat shields vibrating at a certain resonance as that's what it sounds like however with AC on it goes away.
Any ideas?

 

[Blurem]

Mate, this is exactly whats happening to me, very annoyed, it kinda sounds like plastic shaking or something along those lines. hope someone knows what it is

EDIT: I have found some evidence to suggest it might be the fan belt, or maybe something to do with the exhaust. I recently got rear-ended, not too much damage, but could it be that?

 

[VPFreak]

I'm going to try taking the belt off and running it while cold to see if it is belt related. My only other thought is it could be the a/c compressor, but then again if it was it would also make the noise in neutral.

Your right though when you say plastic shaking noise as originally I thought it was coming from behind the dash somewhere. I'll keep you posted if I find the source of this noise.

 

[SavVYute]

Suggestion. Try putting a little pressure with your hands on the AC pipes where they run through the firewall and see if it stops it. Also check none of the pipes are rubbing on any part of the engine bay or loose in their mounting clips.

 

[VPFreak]

Ok, took the belt off and silence. Checked all AC pipes and there is no rubbing or vibration from them at all. So I am thinking it is either the tensioner or pully ( neither seem to have any play) or the power steering pump (has some play when you move it in and out) or the water pump (also has some movement when you move it in and out). The AC compressor feels fine. Might have to do a bit of trail and error replacement. I'll keep you posted.

 

[VPFreak]

Ok, it seems that it is the AC compressor. The series 1 Commodores have a clutch less compressor which is basically always engaged, so I am guessing something inside is rattling at those a particular revs. So now I'm tossing up whether I just live with it, or wait for the compressor to die and then get it replaced. Anyone know a good AC service place in Melbourne south east area (Moorabbin)?

 

[VPFreak]

I thought I would update this thread for some closure in case anyone is experiencing the same problem.
If you pull the compressor clutch plate off you will find 6 rubber bumpers in there. These wear out over time and the compressor then rattles. I guess this is why it didn't do it with the AC on as it was under tension.
Anyway you can find these on eBay or I bought them from a place called Mavoyparts just google them.
The compressor is a Denso 6seu16c.