Technical Inquiries: March 2005

Q&A Column Changes

If you check the Contents page for the location of the “Technical Inquiries” column in the April 2005 issue of FMC magazine, you won’t find it listed. No, we’re not playing an April Fools’ joke on readers. Starting with the April issue, we will welcome Gary Bunzer and his RV Doctor question-and-answer column to the pages of FMC magazine. Gary’s new column will be called “House Calls with the RV Doctor” and will focus on questions related to the “house” portion of a motorhome. Other questions will be addressed in a column that we’ll be calling “Tech Talk.” These columns will take the place of the “Technical Inquiries” column, and, like that column, they will appear near the front of the magazine each month.

Q: The “Recall Corner” section of the September 2004 Technical Inquiries column (page 24), seems to imply that air-brake systems apply the brakes using air pressure. Has something changed? In every dump truck we drove over some 45 years, the brakes were kept off by air pressure, not applied by air pressure; strong springs applied the brakes when the air was let out of the bladder by pushing the brake pedal. Can you please let us know? Thanks.

Camilla Van Sickle & Bill Pennington, F169256
Tonopah, Arizona

A: You are correct; when the brake pedal is depressed, air pressure is released, allowing the springs to push the brake pads or shoes against the discs or drums. The springs hold the brakes on until air pressure is built up enough to release them. That’s why the brakes are applied should a catastrophic failure occur in the air pressure system. The wording should have been slightly different. Thanks for the heads-up!
“” J.B.

Q: I’d like to pass along some technical information to other FMCA members. I have a 2001 Itasca 35U motorhome that is equipped with a state-of-the-art electrical system called the PowerLine Energy Management System and 50-amp shore power. The PowerLine system manages power by shedding appliances (shutting them down) if the incoming power falls below 50 amps so that circuit breakers aren’t tripped. In the 50-amp mode, however, it will allow everything to work at once, or so I’m told.

It became apparent to me, though, that it was only operating on 30 amps, even when connected to 50-amp shore power. I contacted Winnebago Industries and was told that something in the unit was not connected properly, which they solved almost immediately.

The problem was with the circuit breakers. There are five double circuit breakers (10 switches for 10 circuits). With this system, the last double breaker should have been two single breakers. Winnebago shipped me the correct ones and I snapped them in myself. What a joy it was to finally see my 50-amp service light come on for the first time!

If someone out there is having a similar problem with his or her coach, contact the manufacturer; the company will be glad to help.

Leo Bessette Jr., F41563
Pawtucket, Rhode Island

A:  Thank you for the information.

Q: Is there a motorhome tire made with more than one-ply sidewalls? I have a 36-foot Holiday Rambler Admiral motorhome with Michelin tires. This past summer in the Cape Cod area, while the coach was parked and on leveling jacks, the right rear inside tire blew. It had a hole in the sidewall big enough to push a tennis ball through. I know the air pressure was where it should be, because I had checked it recently. I have two other motorhoming friends who have had similar experiences with the inside rear tires of their motorhomes “” one of them had two blowouts between Florida and Massachusetts. I hope you have an answer to this type of problem.

Dick Morris, F207006
St. Petersburg, Florida

A: Suffice it to say, every motorhome tire is rated at more than one sidewall ply. Rather than go into details on RV tires here, I’ll refer to two stories that previously appeared in the magazine: “Tire Safety” (April 2000) and “Weight And Tire Safety” (September 2003). These articles cover many aspects of tire safety.

However, I will say that all indicators point to the inside right rear tire as having more problems than any other tire position on a motorhome. The reason for this belief is that the outside right rear tires on motorhomes tend to leave the pavement while on the inside of curves and on highways with shoulders that are lower than the road. When an outside rear tire loses contact with the pavement, the entire weight of the right rear corner of the motorhome presses down on one inside right rear tire momentarily. Over time, this will affect the sidewall integrity of the tire and potentially lead to a blowout. This is why, if you’re certain your air pressure was correct, you should have your coach weighed at the earliest opportunity. Don’t just determine the overall weight; weigh it per axle and per side if you can (this can be done for a nominal fee by Recreation Vehicle Safety Education Foundation personnel at any FMCA convention and some FMCA area rallies). Make sure the weight of the motorhome is distributed evenly without overloading any one corner. In addition to weighing the coach, you must regularly rotate the tires, including the spare, to spread the tire wear around. Also check the dates of tire manufacture and buy new tires approximately every five to six years. And once you’ve weighed your coach and determined that it’s not overloaded, make certain that the stated load range of the tires is well within the weight of the coach.
“” J.B.

Q: Congratulations on your magazine; I read it faithfully every month. A while back we noticed that the center of the floor in our 1998 motorhome was coming to a peak. When we look at the floor from the front of the coach, the center is higher than the edges. It has been getting worse over the months. Is it because the sidewalls of our RV are dropping? Has anyone else had this problem?

Terri Bouchard, F227369
Prevost, Quebec, Canada

A: From your description it sounds as though this could be the result of panel delamination. As I am not directly familiar with your problem, I only can provide some general information on the subject.

Body-seam sealant(s) may degrade over time, depending to some degree on the quality of the original application and/or the amount of intense exposure to direct sunlight, along with other factors, such as the amount of body twist produced by your motorhome as it is going down the road. If water makes its way through an improperly sealed opening on a laminated panel (i.e. doors, windows, and storage compartments) and seeps behind the walls and under the flooring, it can cause the laminate to expand and the panel layers to separate over time, causing them to bow or bulge. RV owners must be ever alert to possible internal water leaks that would produce the same results. While plumbing is mainly out of sight, most plumbing and fixtures generally are accessible. (A water pump that runs when there has been no demand suggests an internal leak.) Also, an external water source of unregulated high pressure may cause a small leak. The end results are all the same. RV owners need to read their owners manuals carefully and to follow all maintenance procedures for various systems and components.
“” R.H.

Q: My generator starts very easily when it is cold. But when I pull into a rest stop after driving for a couple of hours on a hot day, it just cranks without starting. If I pull into a campground and try to restart it after waiting a couple of hours, it starts fine. It is a propane-powered Onan 6.3-kilowatt generator in a 1988 Beaver motorhome. It has 416 hours on it and was last serviced at 386 hours. Can you help me with this problem?

Carroll Causey, F97872
Upland, California

A: I think the problem is that the propane supply line becomes too hot and the liquid propane in the line vaporizes. This condition is similar to a vapor lock on a gasoline engine. As a first remedy, I suggest that you insulate the line between the tank and the regulator wherever it may be exposed to heat. If that doesn’t work, schedule a service appointment for a hands-on diagnosis.
“” B.H.