House Calls with the RV Doctor
By Gary Bunzer
Dear RV Doctor:
My girls and I just purchased a 1985 Minnie Winnie. We took our first “shakedown” trip and discovered two issues. First, the water heater: the burner will light and produce hot water, but, unfortunately, only about 2 1/2 cups (no warm shower for me)! I went to the RV store and was told to replace the thermostat and the overheating sensor, which I did. Nothing changed. Any suggestions? Second, the pilot light in the oven will light but not come up to temperature. I’ve been told two different things: first, that the thermostat was bad and needed replacing (very expensive), and, second, that the pilot light assembly needs to be cleaned. Care to weigh in on these two issues?
West Richland, Washington
RV Doctor: Stephanie, if you’re serious about having only about 2 1/2 cups of hot water produced by the water heater, I’d be tempted to suspect that your water heater is equipped with a bypass valve system that isolates the water heater from the rest of the fresh water system for the sole purpose of winterizing. Isolating the water heater eliminates the need to fill the heater with antifreeze during cold weather storage. The valves will be located at the rear of the water heater, that section that extends into the motorhome “” probably located under a cabinet or closet. You may even have to remove an access panel to see them. Water heater bypass valves weren’t that common back in 1985, but some astute RVer may have had an aftermarket set installed somewhere along the way. They are (or should be) pretty much standard now. Even with the valves closed, it’s still possible for radiant heat to migrate and warm a little of the water in the bypass line. If you’re being a little facetious (easy to be with daughters; I know, I raised two myself), then I would suggest a possible blockage in the hot water line going to the shower. This can be verified if indeed you have plenty of hot water emanating from the galley or lavatory faucets, but not in the shower.
A third possibility is that you have an inordinate amount of calcium buildup in the heater tank due to lack of maintenance over the years. The water heater should be flushed and cleaned regularly to keep particles from coagulating inside the tank. This, too, can be verified by removing the drain plug (or opening the drain valve) located on the outside of the water heater. Open the pressure and temperature relief valve or open all the hot faucets inside the coach; the draining water should be clear and flowing steadily out of the drain opening. If it simply trickles and small white particles and a milky residue exist, then the heater tank may be full of buildup, and the inner tank should be replaced or, because of its age, I would recommend a brand-new water heater be installed. I’ve cut open older heater tanks in the past and have found some of them more than half-filled with deposits and calcium-like chips. As for your second question . . . keep reading!
Oblique Oven Operation
Dear RV Doctor:
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 4 years old. The problem is that the oven will not maintain the temperature. When it reaches its selected temperature, the burner will shut off and never come back on. 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 temperature to 450 degrees Fahrenheit 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.
RV Doctor: Gary, operational issues with any of the four LP-fired appliances common to just about every RV hinge on two very important facets: cleanliness and the correct amount of LP-gas pressure. By verifying these two aspects, one can then begin a proper track of troubleshooting.
The incoming LP gas 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 be affected by 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, be sure the delivery line pressure is set correctly at 11 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 percent capacity while making the adjustment. Many RVers are equipped with a water column manometer and have the wherewithal to make their own adjustments. 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 the pilot orifice is clean and free from debris and spider nests, etc. Though very little maintenance is 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 moisture is found, you will have to purge it 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 is 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 in such a way 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 sense 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 oil or grease, thereby rendering it inaccurate. This device lets the oven thermostat know that the desired temperature has been reached.
Finally, 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.