if jou have an instrument that can measure +12 volts , just measure behind the switch and see if jou get 12 volt tru the switch , if jes go a step further , the fuse box , do there the same if jou have +12 volt there go further to the light , if there is no current going to the light , jou need to look between the light and the fuse box if the cable is not broken , sometimes those lights take there minus from the chassis , look if that connection is stil good , there can be no rust on that connection or untherneed , if jes , clean it , sand it , and remount it whit copper grease on it