Frustrated with motor head.

\015 I have a Dyson 21 for the past three years and loved it until recently. The motorhead keeps shutting off. So I cleaned the filer, let it dry the 12 hours, and even bought a new motor head for $150. I tested it today and it still keeps shutting off. I checked the hose for obstructions (which there were none), made sure everything was cleaned and NOW I am at a loss. What else can I do?????\015 – Dyson DC21 All Floors Stowaway HEPA Bagless Canister Vacuum – Iron/Titanium/Yellow