Aha! Here I can help. Regular user replaceable vacuum belts should be checked periodically (every few months) and probably replaced roughly every six months to a year depending upon the amount of use the machine gets. (Special belts, cogged or made of long-lasting material may require less frequent checks and changing.)
As regards standard rubber vacuum belts, the ideal is to change them before they need changing -- just like the tires on our cars.
The good news is that vacuum belt replacement is far less expensive deal than getting new tires.
My best advice is this, take the machine in to local vacuum repair shop and have someone look it over and give it a tune-up/cleaning. As you haven't checked the belt in four years, I kind of guess you may not have changed your machines internal or exhaust filters. That too might be contributing to the problem.
After a local vac person has checked out and serviced your machine, which shouldn't cost much, have them carefully explain what they found. Also, look for your vacuum's user guide. If you've lost or misplaced it many vac makers still provide manuals for previous models by way of download.
A regular maintenance check is not a big to-do and will help keep your machine running at its best. Take a quick look at internal and exhaust filters after every couple of bag changes and don't allow bags to pack all the way full with dirt. By the way, what brand and model do you have?
Best,
Venson
BEFORE you go into a repairers check the following.
When the upright is on its back, check to see the roller brush is revolving at high speed. If it isn't then the drive belt will need to be replaced or there is a clog.
In my experience if an upright isn't picking up it could be a myriad of reasons. Switch off and take the sole plate off the bottom - is the roller brush clogged up with threads and hair? Remove it all and also check the main dust channel which is usually to the left or right of the upright. On some brands you can remove the entire dust channel but if its an old vacuum then just check with your fingers that nothing is clogged. Also check if you can, the main dust channel leading to the dust bag. Sometimes older uprights with a kinked hose at the bottom can get clogged.
