try using a jumper across the thermostat connection on the gas valve. (unless the t-stat is in series with the power source, then jump the wires at the t-stat.). are camper units 24volts, or 12 volts? if 24, you may need the inverter running. when you say the fan is working, is it turning on by itself a set time after the t-stat calls for heat, or are you running it with a "fan" switch? a mud dauber would be able to clog the burner, so remove the burner line from the gas valve and blow through it. (i think on campers the burner comes out with the line like a water heater, correct?) you should be able to feel/hear the air blowing through the jet. does the pilot stay lit after the call for heat? good luck!