If you find that your Dyson vacuum is pulsing on and off, this may be an indication that there is a blockage somewhere in the system. The instruction manual should give you more information on how to take your Dyson apart to check for obstructions, but if you find an issue that you are unable to solve yourself, you can organize a service directly with the company. Remember, if you have a cordless vacuum, the issue may be as simple as the device having run out of battery and needs recharging.