R4 compressor vibration

[toddball]

I've always had a vibration between 700 to 900 rpm with the ac compreseor running. I've tried different belts, new compressor. I have all the factory brackets. The belt always gets a standing wave vibration. I'm using a gates 7545, an inch shorter than factory. It seemed worse with the 7555 belt. From what I've reserched it is a problem with these r4 compressors and v belts. Any ideas to try?

I have the idle solenoid for the carburetor to bump the rpm and I can set it to help avoid the vibe but would really like to figure this one out. Basically, it's the only thing on my K5 that I've never been able to figure out.





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[6872xtc]

As far as I know, the idle step-up solenoid is the easiest solution. I have found them on lots of factory installations. TBI even bumps the idle when the A/C is on. I have a '95 K2500 that the R4 growls at idle when the head pressure gets up a bit.

I put a Sanden on my '90 Jimmy because I got tired of the problems with running an R4. Seems like I can't have one last more than 2 years without some sort of problem. But the Sanden required adapters for the serpentine bracket and then new lines. You would probably have to change the brackets completely.