Took a long trip this weekend; about 300 miles/day in three legs. Car ran perfectly the whole trip except for the following, which tightened my cheeks when it happened:

Going about 55, heard a terrible squeal and pulled off the road. Squealing continues so I turn off the engine. Restarting was without incident; I have oil pressure, good temps and no alternator light, so I conclude its the ac compressor. No choice but to keep driving. We drive another 150 miles without a/c. It happens again without ac, so I finished the trip with the ac on. We thought it was coming from the rear. Both moving and stopped. I cant say if it was related to the engine running or not. Sunroof was closed, radio antenna was down, and doors were locked the second time and not the first.

But I'm thinking its the aux vacuum pump. It was loud. It wasnt the running gear. Why would it activate and how do I test this theory? I tried the locks a dozen times at home but couldnt recreate. Could the antenna decide to lower itself when already lowered and scare the stuffing out of me? Anybody want speculate? (I know you do!)