Check the voltage of the RV furnace. RV furnaces fail when the voltage is below 10.5 volts. If there is no power going to the furnace, there may be a problem with the generator.
Check the pilot light. Pilot light failure is one of the most common problems of the furnace. To resolve this, first make sure there is propane and that it is on.
Make sure the pilot light control is fully depressed. The gas pressure regulator should be set to 11 inches of water-column pressure.
Make sure the igniter gap is 1/8 inch. Try purging the air out of the lines and make sure the orifice is not clogged.
Turn off the propane and replace the gas controller. Make sure you have the exact replacement. As you remove the wires, mark them so you know where they go when replaced. Remove the control valve. Replace with a new valve in reverse order. Test for LP leaks by turning on the heater and propane gas.
Check the thermostat, battery voltage and sail switch if the burner does not light. If it still doesn't work, it could be a clogged burner. Check to see if the flame sensor is set correctly, clean and not corroded. If the flower fails, check the 12-volt fuse or for low battery voltage or crossed wires.
