Hi Debbie, The vacuum cutting in and out is a key indicator of either air blockage, or the brush in the vaccum head seizing because of a build up of hair and fluff. Using something that is strong but flexible, check the vacuum head behind the brush, (remove the brush if you have to), where it goes up into the tube. I had a similar thing happen to mine, and it was only then was I able to see the blockage that was fully contained in the bend between the tube and the vacuum head. Also, if you haven’t washed out the air filter, the long tapering filter element going down the center of the vacuum head, that can also cause the device to cut in and out, but it generally does it all the time regardless of the fitting attached. When these work they work well, but they also require a bit of preventative maintenance especially for the brush head to keep them at their optimum; especially if either pet or human hair is common.