Test procedures will vary on model, manufacture. Easiest thing for you to check right off the bat is start the generator, make sure all the breakers are turned on, plug a drill into the outlet, and see if the drill starts, if it starts generator is fixed. If it doesn't start grab the chuck with your hand and turn the chuck backwards rapidly. I just give it a quick twist. Some people will put a 1/4 dowel in the chuck and put the other end in a cordless drill and use the cordless to turn the chuck. If that doesn't start the power, than it could be everything from bad capacitor, to bad voltage regulator, to bad brush, to shorted armature or rotor. Will require resistance testing to comfirm the actual problem.