I did some searching that did not lead to an answer. I have an air filter light that flashes and beeps every now and then. I changed both filters (inner looked dirty) but on my short drive after changing the filters, it went off again. Should I test the vacuum switch next? Any info on what I should be looking for? This SS is new to me so I have been putting together list of parts to order from messicks. Not sure if I will be needing to ad a vacuum switch to it. Thanks to Mike10. I found an older thread that related to the exact same jerky conditions I am having with my machine. Found one of the front plate bushings gone and the other very loose. Got 2 of them in my cart!