Dear Doc,
My problem is with my Atwood oven. It has never worked right from when I got the RV new. I took it back to the dealer and they made some adjustments, but it still doesn’t work. It is now four years old. The problem is the oven will not maintain the temperature. When it reaches its selected temperature the burner will shut off and never come back on. When I first light the pilot it takes about two to three minutes of holding a match under the pilot to light it. When the pilot does light the flame sputters for a couple of minutes then it seems to burn normal. I set the oven temp to 450-degrees or so and the oven will go up to about 350-degrees and then the burner goes out. Sometimes the pilot will go out also. My other appliances seem to work okay.
Gary Schiff, (Middleton, MA)
Answer:
The incoming LP is very important, especially in smaller burners such as pilot flames. The relatively large orifice of the main burner in a water heater, for example, will hardly notice any difference in minimal discrepancies with the delivery pressure. But to the oven pilot burner, it will have a more dramatic and negative effect.
First thing, be sure the delivery line pressure is set correctly at 11.0-inches of water column. The only way to accurately measure this pressure is to use a water column manometer and to load the main LP regulator to about 50% capacity while making the adjustment. Many RVers are equipped with a water column manometer and have the wherewithal to make their own adjustments, (especially if you’ve attended one of my seminars). If you have not had prior training in this important step, simply make an appointment at your local RV service shop and have them set the pressure for you. They should also perform a perfunctory LP leak test at the same time.
Second, be sure that pilot orifice is clean and free from debris and spider nests, etc. Though there is very little maintenance necessary on the typical RV range, the pilot orifice is one of the important areas to consider. Since you mention the appearance of sputtering at that pilot, I would suspect insufficient LP pressure, a dirty orifice or possibly the presence of moisture in the LP source. If you can verify the correct pressure and eliminate a partially clogged orifice, have an LP supplier investigate the possibility of moisture in the LP container. If found, that moisture will have to be purged from the container and the system. This seems unlikely since you state no operational problems with the other appliances.
When the delivery line pressure is properly set and the burner orifice free of any obstructions, next look for the proper positioning of the thermal sensing bulb at the oven pilot assembly, (see photo). It should be positioned such that when the pilot flame is enlarged (when you set the oven thermostat to the desired cooking temperature) the pilot flame fully engulfs the body of the bulb. This opens the oven safety valve, allowing LP to enter the main burner where it is ignited by the pilot flame. If the thermal bulb is out of position, it may feel the extended pilot for a few minutes, but with the disturbance of air inside the oven when the main burner ignites, the flame may move slightly away from the tip of that thermal bulb. Thinking the pilot has been extinguished, (perhaps it has), the oven safety valve will shut off the gas supply to the main burner.
Another component to check for cleanliness is the oven temperature sensing bulb inside the main compartment of the oven. Located at the rear and upper portion of the oven, it can become coated with cooking oils or greases, thereby rendering it inaccurate. This device lets the oven thermostat know that the desired temperature has been reached.
Lastly, you could simply have a faulty oven thermostat. If the pressure is set properly and all the above-mentioned components are clean, this is where I would focus my attention.
(Please feel free to comment, however, please also note that due to the volume of communications I receive from multiple channels I cannot guarantee a personal response in every instance. However, questions of an overall general interest may be considered and published in an upcoming RV Doctor column.)