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RV Doctor ColumnRV Doctor #337 Dear RV Doc, I have a Pace Arrow with a Chevy 454 engine. I purchased a Prowatt 300 inverter and plugged it into the cigarette lighter. The Prowatt works fine until I start the engine. It then faults like it is in an overcharge condition and quits supplying power. If I turn the engine off, the Prowatt will resume normal operation and work fine. I tried it on the lighter plug in the back bedroom with the same result. I hardwired it directly into each one of the batteries, Starting, Coach and then Aux. Same thing happens! No matter what I try, the Prowatt will always shut itself down when I start my engine. I have tried every test imaginable, but it simply will not operate with the engine running. But when I plug it into my 2000 Ford F-250, it works perfectly regardless if the engine is running or not. I have called Prowatt and they say the unit is not faulty, but instead is detecting an overcharging condition when my RV engine is turned on. Please help? Why does the Prowatt keep shutting off? Am I producing to much current? Bob Terry, (Renton, WA)
Bob, given that the unit works correctly in your F-250 and also when the RV engine is not running, the inverter is obviously in working order. The fault only occurring when the engine is started and running, leads me to question the alternator. Perhaps the alternator is putting out higher than acceptable DC voltage when running. If I'm not mistaken the Prowatt 300 shuts down around 15.0 to 15.5-volts DC. A voltage exceeding this is possible with some alternators, especially ones with poor or nonexistent output regulation. Voltage this high is not good for batteries or other DC appliances. If there have been other problems in these areas, such as off-gassing at any of the batteries, it would be confirmation of alternator regulation trouble. I would recommend you measure the voltage at each location before and after the engine is started, looking for high voltage situations. It would also be nice to capture the voltage history over time during engine start up, but this is only possible with sophisticated scopes which are not usually found in RV shops. Hopefully the voltage readings alone will give some indication as to the source of the problem. Alternator output in the form of ripple voltage is also hard to see with a common VOM (volt-ohmmeter), but could also be the cause of the fault in the inverter. There just may also be a voltage spike that is causing the inverter to shut down. The spike may only be a temporary phenomenon existing only during engine start up. If this is the case, resetting the inverter by turning the switch off for a few seconds and then back on, should help. The most obvious solution is to improve alternator output voltage regulation by adding an alternator regulator, such as the Xantrex Alternator Regulator (XAR) or by upgrading the entire alternator to a better regulated model. Any new alternator should be of the high output variety. The added benefit of this will be cleaner and faster battery charging with longer battery lifetimes. This is my best guess without the benefit of checking the system with a scope.
Dear RV Doctor, I've been looking into air ride hitches. I have GMC dually and a 30-foot 5th wheel travel trailer. I am looking for a safer, smoother ride while towing. Some of the road surfaces jerk the trailer so much it seems like something will break. I've seen variations from $1000-$2200. Do they really work? Is it worth the money? Joe Tobin, (Endicott, NY)
Though I do not have direct experience towing a fifth-wheel, Joe, I have studied many of the accessories and add-ons available. I have looked closely at the Trailair Air Ride pin box and am impressed with its design. I have spoken at length with the president of the company and feel this is one that may actually work quite well. It certainly warrants a closer look. But only you can make the subjective decision as to whether it will be cost effective though. Check them out at: www.trailair.com.
Dear Gary, I tow a boat behind my motorhome and have two 12-volt batteries in it wired in parallel. I also have an on-board charger for a bank of two. I have not used the on-board charger yet as I don't dare hook it up since I don't know what it will do. There is a positive and negative wire for one battery. Can I use this charger with both batteries in parallel or do I have to separate them and charge each one individually? Bernard Machia, (Stowe, VT)
Bernard, as long as the two batteries remain wired in parallel it is safe to use the charger as long as the output is 12-volts DC. Batteries in parallel, regardless of how many, are simply recognized electrically as one "big" battery. Parallel wiring still produces 12-volts, but with multiple batteries in parallel the capacity to store the current is increased. It's the same voltage (12-volts) that pushes the current. It is a good choice. I always recommend as many batteries as you have room for and have the capability to keep charged. Remember that the more batteries you have in parallel, the longer it will take to charge the complete bank. Be sure the charger has the output capability to handle the added storage capacity.
Dear RV Doc, while driving, my gray water holding tank dropped down and ground a hole in one corner from dragging on the ground before I could stop. Are there patch kits for ABS tanks? How do I go about repairing the tank without replacing it? Thanks! John Ashpaugh, (Garden Grove, CA)
John, though many patch kit makers extol the benefits of their products quite convincingly, experience has taught me that the only way to permanently repair a plastic tank with bottom damage is by welding. However, I do recommend the patch kits for small holes located on the top of an ABS tank. Though a bottom corner hole would indeed be tricky, a good plastic welder should have that repaired in a relatively short time. Some, but not many, RV repair facilities offer professional plastic welding services. You'll have to call around to find one in your area. I know a few near where I live but, unfortunately, know none up your way. If you happen to find a service center that has the professional equipment, but no knowledge of how to use it, (it happens), I do offer an instructional videotape that details the steps necessary for successful plastic welding. Feel free to email me if you are interested in the training video. Relatively inexpensive plastic welding devices are readily obtainable for you to attempt this yourself if no shop near you is properly equipped.
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