I have a concord 80 plus gas furnace it will not run. Trouble light does not light.I have power to furnace. No voltage to thermostat. Does furnace have internal fuse. Model #rgu80a100d14-3a

If there is no power to the control circuit board the led light won`t work,also there will be no power to the tstat. If you are sure there is power to furnace check for power coming from the door switch to board,if the door is off there will be no power,in furnace, the door switch itself could be bad .
Let us know what you find