Beginning this fall, I've noticed a loud "thrumming" or droning sound coming from under the hood of our '97 Trans Sport that didn't used to be there - only with the a/c compressor engaged, and proportional to engine speed. Sometimes I even hear the same sound emanating from the rear a/c evaporator (interesting front-to-back stereo effect!)
Although the a/c still seems to be working, this sound suggests that something's not happy - compressor bearing? low refrigerant? Should I get this attended to asap, or can I wait til next summer?
Any advice anyone has to offer would be appreciated!