Despite their high velocity and intense suction power, vacuum cleaners don't actually operate at high temperatures. While it's certainly common for a freshly vacuumed area of rug to feel warm to the touch, the machinery itself should never get so hot that you smell smoke. Any kind of burning smell coming from your vacuum is not normal and is a major red flag that something is wrong.
If you notice a burning smell coming from your vacuum, switch it off right away and try to diagnose the problem.
Look for these three signs, and based on what you see, you should be able to determine the culprit.
1. Do You See Smoke?
Multiple things can cause a vacuum cleaner to smoke. The electric motor can run too hot, the drive belt can jam, or a lighted cigarette end has been sucked into the machine and is smoldering inside the bag.
The electric motor smoking isn't always one caused by one thing, nor is it always obvious. A vacuum motor runs hot if the filters are blocked or if the vacuum bag is full. Clean the filters at the intake end of the machine, and empty the bag.
Upright cleaners have a belt-driven rotary brush at the head of the machine. Check that the belt is still in position and that the rotary brush turns freely. You may find that a large piece of debris has been drawn into the front of the machine and jammed the drive belt. The friction of the drive pulley on the electric motor and the drive belt will create a great deal of heat and a burning smell.
If you've vacuumed up an ember from a cigarette or other flame, the only way to deal with it is to empty the vacuum cleaner bag. Fortunately, most of the dirt your vacuum cleaner bag contains is unlikely to burst into flames when you remove the bag from the cleaner, but you should be careful in disposing of it.
2. Is Your Cable or Wall Plug Hot?
A hot cable or wall plug can be caused by an overworked motor.
After cleaning the filters and emptying the bag, run the vacuum cleaner again to see if the cable or plug gets hot again.
If the either the cable or plug gets hot, it means that there is a loose connection between the vacuum cable and the mains. Check that the wires from the cable are held tightly in the terminals in the plug. This should solve the problem.
If the plug still gets hot, check that there is a tight fit between the plug and the socket. If it is difficult to tell, plug the vacuum cleaner into a different socket. If the plug still gets hot, you need to seek help from an electrician.
3. Has Hair Gotten Tangled in the Rotary Brush?
Hair may get wrapped around the ends of the rotary brush and pulled in toward the bearings. The friction against this hair can create heat and produce a burning smell. The hair will have to be cleaned out thoroughly.