Hoover windtunnel U6476-910 switch doesn't work

What has worked for me on this vacuum is once the handle is off and the on-off switch is visible, work it back and forth manually.  Mine was very stiff and it did not get any better.   I went to radio shack and bought a spray can of Control/Contact Cleaner and Lubricant. It comes with a small piece of tubing.  I put the tube into the top edge of the switch and pushed the button FOR A FRACTION OF A SECOND and then did the bottom edge of the switch.   I worked the switch manually a couple of times.   I repeated the spraying one more time and the rocking.   I put it all back together and has been working fine for me.   This stuff is made for electrical contacts...  HOWEVER, use it very very sparingly!!!  ALSO, a new can has a bit of pressure so watch out that you don't blow some back at you.   JOE

This has happened to me on at least two of my well used hoover windtunnels that I've owned. Easy fix: take the handle off and tightly wrap duct tape or electrical tape around the black plastic "switch rod". Doing that will make it thicker and thus able to activate the on/off switch again.

Likely the switch rod (part 10 on parts diagram) is bending and/or switch is getting a little stiff. Take two screws out of handle and pull towards you (as you stand behind vacuum). Upon removal of handle assembly, actuate on/off switch with your finger. If it is smooth and free, you can try replacing switch rod. If you're handy, you can glue a piece of (plastic/metal/wood) behind the switch rod like I did to act as a backstop/boss. This will hold the cheap plastic switch rod in firm contact with the red on/off rocker switch. If the switch seems sticky or hard to flip by hand...it's likely the culprit and needs replacing. This happened to both my mother's and grandmother's identical units.

Sounds like you have a faulty switch or the actuator inside it is not functioning properly between contacts for ON and OFF. Best bet would be to go to a local appliance repair center and just get a new one.. They are pretty easy to remove and replace.. ( obviously while it is NOT plugged into a power receptacle)..