Did you install old or new dimmers? Is the wiring new? If so, did you verify its correctness? Are the overhead lights florescent?(won't work with a dimmer) Is the wattage rating of the dimmer more than or equal to the light wattage? (it needs to be)The dimmers may also just be blown, and need to be checked. Also if you put the 2 black wires together that are normally wired to the dimmer, then the light should stay lit.