First, if it runs without a bag, there's a problem with the bag lock-out switch or wiring. This needs to be replaced/repaired by an authorized Aerus Electrolux technician.
First, turn dial on top of vacuum counter-clockwise so the smallest dot lines up with the arrow. See if it stays on. If not, detach hose and turn vacuum on. Place palm of hand over intake. If it turns off, it's possible that the tubes connecting to the CVA are clogged and simply need cleaned. This is most often caused by using "made to fit" Electrolux bags. Dust is sucked through the bags and into the motor compartment of the machine. All interior parts get covered in dust and need to be cleaned. If this is the cause, the vacuum is best cleaned and repaired at an authorized Aerus Electrolux store. If the vacuum shuts off, or won't turn on before placing hand over the intake, it's probable the control valve assembly is bad and needs replaced.
Another cause is an overheated motor due to clogged screen at back of bag well, full or clogged bag, dirty afterfilter, bad wiring/connections, clogged hose, clogged power head, or bad motor. It depends largely on the type and model of cleaner. Clogged wands are also a possibility, but unlikely.
Check and clean screen at back of bag well.
Replace bag. Make sure it's a genuine Electrolux bag made by Home Solutions.
Check and replace afterfilter if necessary. These should be replaced after every six bags.
Broken and worn wiring connections are often found in the hose ends due to abuse and normal wear and tear. You can check the continuity of the hose using a continuity tester or multi-tester. If a multi-tester, turn dial to one of the Ohm settings. Place one probe into one of the terminals on the end of the hose. This will be referred to as T1. Touch the other probe to each of the terminals/connections on the other end of the hose. These will be T3 and T4. One of them should read zero, the other should read infinity. Repeat this with the other terminal, which will be T2.
Drop a marble in one end of hose and let it roll through. If it doesn't roll through, the hose is clogged and needs to be cleared. Plug hose into the exhaust port of the vacuum, place other end in the in port. Turn vacuum on. This provides a blowing and sucking action which should clear the hose.
Detach hose from power nozzle (PN). Drop a marble into the wand end of PN. If it rolls through, it's clear. If not, there's probably a clog behind the brush where the intake opening is. You may be able to reach this through wand end with needle nose pliers, or either end with a knitting/crochet needle or a bent coat hanger.
If none of these "fixes" provide the answer to the problem, it should be taken to the nearest Aerus Electrolux store for diagnosis. Repairs or checks involving disassembly of the vacuum should always be done by an authorized Aerus Electrolux service technician
The store nearest you can be found by following the instructions at the below listed link:http://www.aerushome.com/storelocator/