Thomas, I had exactly the same problem, but with another model. Another posting confirmed how to open the machine - slideing the side rails out. Inside there is a vacuum sensor that has tubes that connect to the cannister and the power switch. I found that our vacuum sensor had a broken plastic backing near the O ring. By disconnecting the tube connected to the power switch, the vacuum continues to run. Once I replace the faulty vacuum sensor, I will reconnect the tube. Bye.
Jim Marston
August 2005