Technical Inquiries: November 2003

Wrangler Wiring

Q: I have a 2001 Jeep Wrangler and would like to wire it so it can be towed behind my diesel pusher. Is there a wiring harness that will plug into the existing factory wiring, and if so, where can it be purchased?

Robert Laird, F321471
Beaumont, Texas

A: RoadMaster (5602 N.E. Skyport Way, Portland, OR 97218; 800-669-9690; www.roadmasterinc.com) makes just such a kit. The Universal Wiring Kit (part #150) contains 30 feet of molded four-strand wire with connectors; 6 feet of molded four-strand wire with connectors; 3 feet of plastic wire loom; a ring terminal; solderless wire connectors; plastic cable ties; and two diodes. The kit contains all of the components necessary to prevent feedback and to protect both the motorhome’s and the towed vehicle’s electrical systems, and it comes with step-by-step instructions. I used one of these kits on my Jeep CJ-7 and found it easy to install.
“” J.B.

Q: I am writing for more information regarding vehicles collecting mileage as they are towed. We purchased a 2001 Chevrolet Malibu to use as a towed car. Before buying the car we understood that it would not collect mileage while being towed four wheels on the ground, but we have found that it does add miles. We remove the fuses as directed and follow the directions for towing the vehicle. After our first trip, we realized it was collecting miles and contacted the dealer. We were told by a representative with General Motors that there is no way to prevent this from happening. We are very frustrated.

Is there someone out there who can tell us what needs to be done when towing to deactivate the speedometer? Where do we go for this information?

Bob & Linda McKinley, F295511
Frisco, Colorado

A: At one time Remco sold a speedometer disconnect to help owners keep miles from accumulating on their towed vehicles while they were being towed. But several states made it illegal to tamper with a car’s accumulated mileage (unless a new speedometer needed to be installed), so Remco discontinued the product.

But according to a Remco representative, the 2001 Chevrolet Malibu will not accumulate miles on the odometer anyway, as long as the towing instructions found in the vehicle’s owners manual are followed. He suggests that you make sure that you are removing the correct fuses and that the key is in the right position. He said a possible reason you may be accumulating miles is that you are turning the key one position too far. If none of these suggestions solves the problem, have a GM serviceperson check the PCM and BCM for functional irregularities. It’s also possible that the computers simply need to be reprogrammed.

If for some reason you are following the towing procedures but miles continue to accumulate, you have a few choices. You can place the Malibu on a tow dolly, which would prevent the front wheels from spinning and collecting mileage, or use a car hauler with the same result. Remember that disconnecting the speedometer cable may be considered illegal in your home state.
“” J.B.

Q: We have a 1993 Holiday Rambler Navigator. It has two 12-volt-DC engine batteries and four 12-volt-DC coach batteries. We have had no problems with the two engine batteries, but the house batteries are a constant problem. They are a source of corrosion that spreads throughout the battery area. Do you have any solution or recommendation on how to control this problem?

Frank Smith, F268303
Las Vegas, Nevada

A: I assume that the batteries are unsealed cell, flooded-type, lead-acid batteries, as corrosion usually is no problem with sealed batteries. Corrosion normally comes from electrolyte vapor seeping out of the cells. Nominal vapor ordinarily will attack only the terminals, but it sounds as though an unusual amount of vapor is escaping and contaminating the entire compartment. This probably would come from the electrolyte boiling during overcharging.

Since the house batteries are being charged by a convertor/charger (or an inverter/convertor/charger), the charge rate and duration may be suspect. To find out whether this is the case, put a voltmeter on the batteries while the charger is operating. The charge rate should top out at approximately 14.2 to 14.4 volts and then reduce to a maintenance charge rate of between 13 to 13.5 volts. If you are not getting these readings, the problem is most likely with your charger. On some chargers, the rates are adjustable “” some are not. If overcharging is not the problem, I would suspect you have one bad battery that is boiling severely.

To determine which of your batteries is causing the problem, have them all tested or just observe them with the caps off. You should be careful whenever you are working with batteries under the conditions described here, because a spark might cause an explosion if an abundance of vapor is present. Wear a face shield, protective gear, and rubber gloves. Batteries can be dangerous if mishandled.

Finally, make sure you’re not overfilling the batteries. The electrolyte should be no higher than the split ring in the well.
“” B.H.

Q: Where can I get information on how to change the rims on my P-30 chassis from the narrow 19.5 tires to the wider ones? I have read a few articles and all seem vague on the subject of the width of the rims. Who can I call to purchase the new rims?

Thomas Guidry, F170591
Larose, Louisiana

A: The Budd Company (now the ThyssenKrupp Budd Company) manufactured the original wheels on your motorhome. Until recently, Ellis Wide Wheels sold wide wheels for the P-30 chassis, but when Max Ellis retired, the original manufacturer, Boxer Wheels, resumed marketing them directly. For information or to order, call Boxer Wheels at (800) 231-0845 or visit the company’s Web site at www.boxerwheel.com. Alcoa (800-242-9898, www.dontpolish.com) also may be able to help you.
“” J.B.

Q: We have a type A motorhome with a gross vehicle weight rating (GVWR) of 20,500 pounds and gross axle weight rating (GAWR) of 7,000 pounds for the front axle and 13,500 pounds for the rear. It’s equipped with Goodyear 245/70R19.5 load range F tires. According to Goodyear specifications, the tires should be inflated to 70 psi all the way around (this is the minimum tire pressure recommended for the tire load range and axle ratings). I have weighed my coach fully loaded, and the axle weights and total weight do not exceed the ratings, so I’ve kept all the tires inflated to 70 psi.

But I have heard a lot of chitchat about how much weight each of the dual tires carries and its effect on tire wear. The consensus seems to be that the inside tire carries approximately 10 percent more of the axle weight than the outside tire. Is this true?

If so, should I keep the air pressure in the dual tires at what Goodyear recommends, or should I increase the air pressure for the inside dual tires 10 percent (to 77 psi) to compensate for the increased load that those tires carry?

Tom & Dottie Nowell, F294887
Fort Worth, Texas

A: First of all, the inside dual tires do not carry more weight than the outside dual tires. If that were so, the inside tires would have vastly more wear. That said, however, many are of the opinion that the inside right-rear dual does carry most of that corner’s weight at times such as when the outside dual tire leaves the pavement momentarily during right-hand curves or even on straight stretches when the coach gets a little too close to the right pavement edge. So, you’ll want to maintain the same cold pressure in all four rear tires.

Using 245/70R19.5 load range F tires, according to Goodyear’s table, 70 psi will provide the weight capacity of 3,415 pounds (dual) and 3,640 pounds (solo), which would handle a GAWR of 7,000 pounds front and 13,500 pounds rear. However, you should still watch for accelerated wear along the outside shoulders, which is an indication of low air pressure. To ascertain what the best pressure is for wear, ride, and handling, try increasing your tire pressure in increments of 5 psi up to 85 psi, and continually check the tires for irregular wear patterns.
“” J.B.

Q: A few years ago, after researching the subject for months, I purchased an inverter from Invertrix Inc. of Ventura, California. Evidently they have now gone out of business or at least don’t seem to be manufacturing inverters. Do you know of a place that may be able to repair my inverter? It seems to have a major problem, and I don’t know where to turn. I really don’t want to have to purchase another brand at this time.

Ron Young
Via e-mail

A: I can find no current listing for Invertrix, so I don’t believe it is a viable company at this time.

Xantrex has purchased a number of inverter companies in the past four years (Statpower Technologies, Trace Engineering, and Heart Interface), but I checked with the company and Invertrix was not among them. The Xantrex representative I spoke with indicated that the company does not repair other companies’ inverters.

One of the other companies listed under the inverters category in the Business Directory may be able to assist you (see the January 2003 or June 2003 issue of FMC or visit www.fmca.com/bd). Or perhaps another reader will have a suggestion for you.