tom o'connor
how much did you pay for it. if it was a cheap one there is you problem or not all light bulbs are dimable try changing the bulb for one that is if neither of above its faulty change it you need to be careful when buying dimmer switches there are a few thing to remember when installing one 1 they are the single most causes of electrical fires so get one with a fuse 2 they have a life span of approx 10 years after which they need to be replaced 3 they have a wattage rating normally 250w collectively (add up wattage of all lights on that switch) hope that helps