I have a vibration in my A/C belt that I can't tighten out. Has anyone heard of putting an idler pulley on that to take out the shimmy????

I did put an idler on my belt but still get some vibration which I think is the rough cycles of the compressor feeding back to the belt. I machined a bracket for it but would still like to come up with another one. E-mail me and I'll try to get you some decent pics.. Also I'm going to try a different brand of belt. WP