RV Doctor Column RV Doctor #300 Dear RV Doctor, My wife and I recently purchased our first RV, a 1992 motorhome which has a converter/charger made by Magnetec. I have noticed that while plugged into shore power, it is keeping the house battery charged, but will allow my engine battery to go dead after sitting for ten days. The vehicle would not start up or crank. I hooked up an external auto-type charger to it which brought it back up to full charge. I disconnected the external charger and tried starting the vehicle and it started right up. I measured 14-volts plus coming from the alternator to the batteries. I stopped the engine and then plugged in the shore power. I measured a fairly constant 12.9 volts coming from the charger/converter at the house battery with different loads placed on it and I watched as the voltage on the engine battery dropped to 12.4 volts. I placed a load on the engine battery to see if the charger/converter would kick in and it did not. The voltage just dropped some more. It would seem as though this battery is not charging from the converter/charger. Any ideas as to what to check and where to look to find what the problem is? Could a faulty isolator cause this condition? Thanks for any help you can provide. Alan Coleman, (Severna Park, MD) Alan, Unfortunately, the converter in your motorhome does not charge the automotive engine start battery. There are some high-end converter chargers that do have such circuitry such as the Statpower 40+. Because of the design and application differences between automotive batteries and deep cycle or RV/marine batteries, they should never, (except in the case of an emergency), be wired or connected together. Some unknowing RVers may run a secondary jumper wire between the two batteries to charge while plugged in or perhaps install a simple solenoid relay that effectively does the same thing, but in the long run, this does more damage to the batteries than good. In some cases, a secondary battery charger can be utilized to keep the engine battery charged while the engine is off, but this mandates close monitoring since most inexpensive, stand-alone battery chargers are prone to overcharge the battery, even on a so called, "trickle charge." I only recommend a secondary charger when you are able to check the water level, (not possible on some automotive batteries), every hour or so. But this is quite restrictive. For "serious" RVers I usually recommend the addition of a Statpower charger to be utilized as a charging device only, for both engine and RV battery banks. Each battery system is independently connected to the charger and is charged separately from the other, thereby maintaining true battery separation. Remember, the addition of the Statpower is for battery charging only. The existing Magnetek will still be the active converter while on shore power. The Statpower series of chargers will more than satisfy your charging requirements and they are switchable for either wet cell, gel or AGM battery designs. That being said, I would still verify why the engine battery depletes so quickly. There are quite a few so called, parasitic current drains on the battery such as radio memory, LP leak detectors, etc. In some cases, the in-dash radio is incorrectly wired to the engine battery. It is best to rewire the radio to the auxiliary RV battery system if you are in the habit of using that device while stopped. In any case, I would suggest further electrical troubleshooting to determine 1) that the alternator is indeed charging correctly and 2) the dual battery isolator is functioning as it should. Unfortunately, troubleshooting those devices long-distance is an impossibility. It would be best in your case to contact a local RV repair facility to perform some preliminary tests. Dear Gary, I usually winterize my travel trailer but the last time, I neglected to remove the racks from the fridge. Now they have some rust on the bars. What can I use to return them to their original condition or is there something that I can coat them with? Thanks, Rob Heath, (White Rock, BC) Rob, Try scrubbing the metal rack carefully with 0000 steel wool saturated with turpentine. Be sure to wear protective gloves and goggles for safety. It may take a few attempts to remove all the rust. After a few applications, wash the racks in warm soapy water and dry with a soft, clean cloth. Next apply a coating of automotive-type chrome polish and buff out with a clean cotton cloth. Depending on the severity it may not be possible to totally eliminate all the rust, but this process should take care of the bulk of it. Dear RV Doctor, What do I need to do to replace the interior ceiling of the roof on a 1974 Dodge Tioga? It's suffering from mildew, neglect and dry rot and needs new support beams, insulation and plywood covering. Where do I find instructions on how to proceed? K.J. Langill, (San Francisco, CA) K.J., It is highly unlikely you'll find the exact instructions for a roof replacement since there are quite a few methods of construction and types of materials used for RV roofs. Such an undertaking is quite daunting for the RV owner to attempt. It is a major repair that will require specialty tools and equipment. To replace just the interior ceiling and a few rafters would not be in your best interest. The deterioration will just continue. It may, however, be a wiser investment to install a completely new roof. The question I have is, is it really worth that expense on a thirty-year old RV? Your existing roof was laid out and constructed on a huge table. It was first framed and the interior ceiling panels were installed and all the cutouts were made, then the whole roof section was flipped over and set atop the side walls and secured. The wiring was installed and the installation was set in place before the top metal was rolled out, attached and sealed. It is doubtful this will be possible to replicate without the proper overhead support equipment common to most RV body shops. Plus advances in roofing materials since 1974 may prompt you to consider the advantages of a solid roof with perhaps an EPDM surface. I feel I must recommend a visit to a well-respected RV body and collision repair center near you to obtain a complete estimate for a total new roof. Weigh the cost against your budget and your fondness for this particular RV so you can make an informed decision. In some cases, a new roof may not be the wisest decision. I wish you luck!
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