RV Doctor Column
By Gary Bunzer
Dear RV Doctor, I recently had a new rubber roof put on my Class C motorhome. Inspecting the roof I noticed several bubbles in it, a couple several inches long, and am wondering if this is normal? It seems to me to be a case of inferior workmanship but I would like to get another opinion before I confront the person who did the work. Your opinion would be appreciated. Tom, (Mansfield, OH)
Tom, bubbles in EPDM rubber membrane are typically caused by improper preparation during installation, water intrusion or the use of incorrect adhesives. With only one bubble on your roofing material I would suspect that spot was contaminated somehow or not prepped thoroughly enough prior to the installation of the membrane. I would definitely let the technician know about it and allow him a chance to repair it. Left unabated, it is possible the bubbling could continue. Look closely to make sure that there is only one. It may be a good idea to mark the circumference of the bubble lightly with a pencil and watch it closely over time to see if it gets any larger. It may be possible to inject adhesive into the bubble with a syringe and re-cement it in place by rolling it out with a hand roller. A small EPDM patch kit can easily seal the injection holes.
Dear Gary, we have a diesel generator on our Winnebago. The generator uses the same fuel/same tank as what runs the motor. How much fuel will the generator use, let's say, in an hour? How can I figure out my gas mileage when using the generator once in awhile? J. Frame, (Clifton, CO)
Janice, when the generator and the coach engine share the same fuel supply, typically the draw tube (dip tube) for the generator ends at about the one-quarter level in the fuel container; this, to prevent the generator from running the tank empty, rendering you stranded. How much fuel the generator consumes depends on size generator you have, how long (in hours) it runs and at what load. The heavier the load, the more fuel consumed. Most all makers of generators will publish a guideline of sorts that will estimate the gallons-per-hour rate at a certain load. Once you have that estimate, calculate the number of hours the generator is used on the each full tank of fuel and simply deduct that amount from your fuel mileage calculation. The result will probably be close enough, all things considered.
Dear RV Doc, I have seven-year-old Rialta and until this year all was fine. Now the generator will start and run with no problem and I can turn on low load lighting without trouble, but as soon as a load is placed on it like the air conditioning or microwave, it quits right away. Any ideas for a fix? H. Greuber, (Tucson, AZ)
Hank, depending on the number of hours on the generator, it just may be time for a set-up/tune-up. All RV power plants require regularly scheduled maintenance. Adjustments to the carburetor and possibly the governor may be in order. A certified RV service technician can quickly diagnose the generator by connecting it to a load bank. RV generators cannot be tuned or set-up by ear and I caution the service technicians I teach that every mechanical adjustment on the generator has a direct electrical consequence. Unfortunately, this one is better left to a pro technician because of the specialized equipment necessary to diagnose it. No load and full load voltages and frequencies must be within spec for the generator to carry a rated load. You can rule out a fuel issue by inspecting the fuel line from the tank connection to the generator connection. Seven-year-old rubber fuel hoses can crack and begin sucking air, which could lead to operational ills when a load is applied. You might also try running the generator from a separate fuel source, then applying the load. If it quits again, you'll know the problem is the generator and not the fuel supply.
Dear Gary, I read your column with much interest and one question regarding inexpensive water heater bypass valves in a recent issue caught my attention as I had a similar problem with my fifth-wheel. In my unit the hot water pressure was very low and flow was slow but the cold water was full bore at all taps. Living here in Calgary I had stored my unit for a lengthy period in a winterized condition and that was exacerbated by a delay in using the unit until the following autumn. After puzzling with it and messing about with the by-pass valves I remembered that I had had difficulty opening one of the valves previously and now I noticed that the cold water inlet valve to the heater opened and closed rather easily. I took all three of the winterizing valves apart and sure enough, the rubber washer on the stem of the cold water inlet valve had come off and was lodged in the seat partially plugging the valve and restricting the flow. I took the valve in question out and pulled the washer and connecting bolt out of the valve and reattached the washer and used some lock-tite on the threads to prevent the screw from coming loose again. Since then I've had no trouble with the hot water flow rate. Thanks for all the good information that you provide. C. Clarke, (Calgary, AB)
Chris, thank you for the information regarding the “less than stellar” valves that are often used in the bypass kits. I’ve been a fan of the brass valves, but it seems all types of valves are somewhat prone to eventual failure. I’m guessing it has to do with the constant exposure to heated water along with minerals and other contaminants in the fresh water system over time.
Send your troubleshooting questions to Gary by filling out the “Ask the RV Doctor” form on the RV Doctor website at www.rvdoctor.com. Questions of general interest will appear in a future issue. Unfortunately, due to the heavy volume of mail received, personal replies are not possible. Additionally, all effort is made to ensure the correctness of Gary’s responses; however, not all answers will apply in every instance. Some situations may mandate a visual inspection and further hands-on testing. It is imperative that if you choose to follow these instructions or procedures, you satisfy yourself thoroughly that neither personal nor product safety will be compromised or jeopardized. If you are in doubt or do not feel comfortable about a procedure, do not continue. Simply call your local RV service facility and schedule an appointment with them.