Antoine, my bet is it's a bad power switch based on what you described is happening. Take note of how the vacuum is wired, then unhook the motor wires, and hard wire them to a old power cord. Plug it right into the wall - if the vacuum powers up, it's either the switch or cord rewinder causing issues. It could also be bad contacts in the cord rewinder too, but you would know that if the power fluctuates by pulling the cord in and out.