Tip of the Day… Furnace. The furnace in an RV is a pretty simple device. It contains a burning chamber, a fan, controller and ignitor. The system starts by turning on the blower. There is a sail switch that detects if it is blowing air. Once the air is detected the controller board opens the valve for the propane and tries to ignite it. There is a temperature sensor that detects the heat. If after 10 seconds no heat is detected the system shuts down in most cases. So for inspecting, first open the outside door and check for bugs. They love the propane smell it seems. Then make sure the propane is one and turn on the heater. Listen and feel for the fan operation. You should then hear the woosh of the propane igniting. Finally the heat should come out of the vents. Pretty simple test.