Hi Jenny, the motor is running okay,does a piece of paper stick to the filters when on?If not,it may be the anti blow back flap above the motor.This is a metal butterfly flap that stops air coming back down the vent hose when off.If the hose is a bit small,it goes inside the connecting ring and stops the flap from opening.That would be my first port of call.All the best.
FOXY, November 2008
