Both the DC04 and the DC07 need constant air to pass over the motors and out of the ports at the bottom of the cyclone. In both cases, the machines are probably blocked. If you are able to find and remove the blockage, remove the cyclone and the post motor filter. Run the cleaner (wear glasses as you will get a faceful of air) and check inside the filter housing. If you see any blue flashing, your motor is arching and terminally ill. It will need to be replaced. The thermal cutout is attached to the motor.
Gordon Smith
September 2006