Monday, June 1, 2015
Posted by RV Doctor
Dear RV Doctor, I am having a problem with the pilot light on the hot water tank on my old motorhome. I can light the pilot light, but when I turn the dial to the ON position, it takes a moment for the ignition, and when the propane gas finally reaches the pilot light area, the combustion is so strong that it blows out the pilot light and the main heating flame too. This unit also has a refrigerator that I can run on AC, DC, or propane. On this unit, with propane selected, after you light the pilot light, it runs and cools the fridge automatically depending on the temperature level that I set it to. I can light that pilot flame, but after that, nothing happens. The pilot light just stays on and doesn't ignite a flame to cool the refrigerator. I believe that both of these problems are related, but I am not sure as to what the fix is. The hot water tank is near the front of the unit, where as the Norcold refrigerator is at the rear on the same side as the hot water tank. I appreciate any advice that you can offer in solving my problem. Dan R. (Howell, MI)
Dan, a couple things to consider; first on the water heater. There will always be a brief delay from the time you move the control valve from "Pilot" to "On" before the main flame ignites. The propane has to travel from the control valve, through the orifice and down the mixing tube, mix with some fresh air, before reaching the pilot flame. The alignment of this mixing tube is crucial. As the gas flows through the tube it draws in air to mix with the propane prior to it igniting. If the tube is not centered on the orifice fitting at the control valve and in line with the angle of that fitting, then turbulence will take place inside the tube and create an improper mixture for combustion. This can cause pilot and main flame outage. Plus the pilot flame should only encompass the very tip of the thermocouple. A too large or too small pilot flame can also lead to pilot outage.
On the pilot model refrigerator, the standing pilot flame will stay small until the temperature inside the refrigerator rises above the setting of the thermostat. If the box is already cooled it’s not likely to ignite the main burner until you open the door a couple of times or put warm food inside. Now if the box is already warm and the main flame will not come on, chances are the thermostat capillary tube is mis-positioned or the thermostat has lost it’s charge necessitating a new thermostat. A few tests by a competent Certified service technician will quickly reveal the exact cause. But most importantly, for both the water heater and the refrigerator, (as well as the other two propane appliances), is the delivery line pressure of the propane. It must be set to 11.0 inches of water column. Being an older coach, it’s probably wise to have a service tech perform a timed pressure drop leak test as well as set the pressure regulator to the correct setting just to be safe. It takes special equipment to measure, set the pressure and to test the regulator, so unfortunately, this is one task best left to the professionals.