The poly-V belt self destructed last night on my '91 350SD, while driving at highway speed with the A/C on. The belt had about 20,000 miles on it and seemed to be in good condition. I put on a new belt and now the A/C clutch is not engaging. Is it possible that the compressor began to lock up and the additional load caused the belt to fail? The vacuum line was severed by the frayed belt. Is there an interlock dependent on vacuum? How do I go about troubleshooting this?
Thanks in advance.

Greg