Vibration from AC Compressor

[Harmon]

AC is blowing good, but when I come to idle, the compressor or belt vibrates make a loud noise...when I take off it goes away.  I replaced the belt but I seem to still have an issue with this.

Plus when the AC is in OFF posisition, the compressor should not be turning on correct?  I feel like I hear it come on, or make noises.

Any info would be appreciated.

Thanks.

[mdws1987]

I just had the same problem on my 87. The noise started after I tried to tighten the ac belt. After several times loosening and tightening, I noticed the noise would go away when I put leverage on with the pry bar in the half inch slot. This was with the motor running. I tinkered with the compressor's bracket bolts and stopped the noise... I wish I could explain what I did but I am not sure. There is bolt on top of the bracket and another on the back. I think I slightly ease the torque on the back bolt to stop the noise. The noise has not returned yet. I did this 2 days ago.

[Harmon]

Hey thanks for the info I will check all my compressor mounts and re tighten belt.  When you were at idle and vibration was happening did it cause your truck to die?

[mdws1987]

No, it did not die.... By the way, the bolt I adjusted is the one at the back of the compressor between the 2 aluminum tubes... I have run the engine several times since but have not taken it out for a drive yet. So far, no noise.

[DrDaryl]

Is it an R4 compressor?  They sometimes "growl" at idle, might raise your idle speed slightly.  As to vibration, belt might need to be a bit looser or tighter, just play around with it.  On my '86 the compressor would run anytime the engine was running, turned out to be the control switch in the dash.