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RV Tech Savvy: House Batteries and Solar Panels

Originally Published in MotorHome Magazine



We have a 2007 Fleetwood Excursion 39S with four 6-volt house batteries. Located on top of one of the air-conditioning units is a small solar panel used for charging the four house batteries. I noticed the small red indicator light inside the coach does not ever light up to show that it’s charging. I checked the voltage right out of the panel on top and it only shows 0.30 volts in bright sunlight.

I have researched this solar charging system and found it to be a 5-watt output unit. I read an online post that said this 5-watt system is basically “useless” and is underpowered for what it was designed to do.

My question is whether to buy the same solar panel ($75) or upgrade to something with a higher wattage output? Should I even bother?

If I go with a different solar panel, can I just mount it and plug it right back in to the two wires up top or would I need to run all new wires with a new controller, etc.?

Bruce Neumeister | Fairfield, Ohio


With four large batteries to “feed,” a 5-watt-rated panel is too small. Based on your voltage reading, it’s also likely that it has failed. Many RVers, including me, like solar panels because they provide essentially free, quiet power, even when there’s no shorepower available. If you store your coach in a location without shorepower, solar panels can keep your batteries charged and extend their service lives.

I would add one or more panels, depending on how often you visit primitive campsites, and install a new controller that is designed to work with the panels. If you only add a small amount of capacity (say, 45 watts), you may need to upgrade the wiring. Just make sure it is heavy enough to handle the maximum output.


Does it Have a TPMS?

When we turn on the ignition and start our 2005 Itasca 31W built on a 2004 Workhorse 8.1-liter gas chassis, a TPMS symbol appears on the dash. Does our motorhome have the ability to read tire pressure sensors on the wheels? If yes, which sensors should we install?

David and Gwen Oren | Via email


No; the only part of the system that came from the factory is a place for a warning-light bulb. If you were to install a tire-pressure monitoring system (TPMS) aftermarket kit, you could conceivably use that light to warn of a tire failure with your added system, provided the kit somehow worked with the dashboard array.


Brake-Switch Question

I have a 2012 Forest River Class C built on a Chevy Express 3500 chassis. I own a car trailer with electric brakes, and I’m currently using an electric brake controller made by PowerStop (500-PS). The controller is activated by 12-volt DC power that comes from the brake switch. It appears that the four wires that come off of the brakelight switch work only in ohms. So, can you tell me where I can connect to a 12-volt DC wire that would activate my brake controller so it can send power back to the trailer to apply the electric brakes on the trailer?

John Riley | Via email


GM has gone to 5-volt DC proportional-type sensors on some of these, so that’s why you don’t get the usual 12-volt DC signals at the brake switches. They act like variable resistance sensors. There should be a stop lamp relay in the underhood fuse block. This is what supplies the voltage to the brake lamps. You can also find the auxiliary stop lamp fuse, which should be 15 amps. Check that the voltage comes on and off at this fuse when you brake. If so, take your signal from the output of that fuse.


Tire Load Ratings

Have a tech question?I need to replace my motorhome’s tires. The current tires are marked load range “F,” but the tires my local dealer wants to sell me are marked load range “G.” Are these compatible?

Larry Simpson | Via email


You didn’t mention what make and model coach you have. Tires with a higher load rating tend to ride a little harder and cost a bit more. The tires should be compatible if they are the same size and the wheels are rated for the load rating and pressure. Never go down in load rating. Going up in load rating can provide a safety cushion, particularly if your motorhome’s tire loads are near the limits of the old tires. This could be helpful if you have had problems with tire failures. However, going to a higher tire load rating does not increase the axle ratings, spring ratings, brake capacity, etc.


RV Tech Savvy

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