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RV Doctor ColumnRV Doctor #317 Dear RV Doc, I have my brand new Fleetwood travel trailer plugged into my home 30-amp shore power. For the last two weeks while loading for a long trip all has been working fine. Today the air conditioner quit. Upon checking the standard power outlets in the trailer with a plug-in polarity tester, the tester indicates hot and ground are reversed! No fuses are blown or breakers tripped in the converter. Shore power is fine. The problem is definitely in the travel trailer. What would cause a hot-ground reversed indication at the trailer outlets? It was quite hot in Texas during this and the air conditioner was working a lot. Thanks for any thoughts you may have on this issue. George Brush, ( Quitman , TX )
George, the first thing you need to do is shut off all incoming power to the travel trailer immediately. Having the hot and ground reversed can be quite lethal. Do not plug the shoreline back in until the problem has been rectified. Hot and neutral reversal is more common, yet still has the potential for a hazardous condition. Hot/ground reversal means the skin on the trailer and the chassis frame are hot! It will be necessary to check all the wiring in the rig to determine where the reversal took place. I'd suspect the air conditioning circuit first, but realistically it could be anywhere in the system. Start by measuring for continuity at the shoreline plug on the trailer. If hot and ground are truly reversed you may have continuity from the hot lead on shoreline plug to the chassis. If that is the case, begin by turning off each breaker one at a time. Once the continuity is lost between the hot contact and the chassis, you'll know which circuit is affected. Once the circuit has been identified, then it will be necessary to gain access to the wiring "make-up" box at the components in that circuit. For the moment, assume it is the air conditioner. At the air conditioner, remove the ceiling shroud to find the box where the Romex cable is connected to the leads on the A/C. Disconnect and separate the black and white wires. Turn that breaker back on and once again check for continuity between the hot pin of the shoreline cord and chassis ground. If continuity is lost, then the problem is in the A/C unit itself. If the continuity is still present, then the problem is in the wiring from the breaker box to the roof A/C. If the circuit with the continuity is a series of receptacles, go to the midway point of that circuit and disconnect that receptacle; again checking for that continuity whenever a component is disconnected or re-connected. Keep dividing that circuit until you find the culprit. If the circuit with the continuity is the converter/distribution panel, then you'll have to dissect that component. If you still have continuity when all the breakers are turned off and you cannot isolate which circuit it may be on, then suspect the shoreline cord connection at the first "J" box where it terminates. There could be many causes - melted wiring in the A/C or that circuit; the GFCI may be miswired; someone may have rewired a receptacle; there could be a chaffed or cut portion on the shoreline cord; a 120-volt AC device may have lost its "bond" with the chassis. Since it was so hot there and the A/C was working hard, I'm guessing the problem could be in the air conditioner. To check that device, attach a short, temporary three-prong plug directly to the A/C wiring at the make-up box and plug it into a separate extension cord on a protected circuit. If the air conditioner operates properly, the problem is in the wiring of the trailer. There are many other tests, such as checking the windings of the compressor and testing the overload device on the A/C, too detailed to list here. And it's doubtful any faults internal to the compressor windings would result in the reversal you are experiencing. It may be necessary to perform an insulation breakdown test also known as a hi-pot test. It takes a specialty piece of test equipment to perform this. If you feel you may not be qualified to perform any of the above tests, don't. Simply make an appointment with a professional shop. Do not compromise product or personal safety.
Dear Gary, my right front travel trailer brake has locked up on three occasions. It always happens when I am leaving a gas station and turning right and applying the brakes during the turn. The brake locks and will only release if I back up a little. The first time it happened it shredded the tire before I realized what was happening. Any advice? Don Lewis, ( Downers Grove , IL )
Don, it is quite possible there is a mechanical problem with some of the components in that particular brake assembly, but you cannot rule out an electrical problem either. In either case, it will be necessary to remove the tire and wheel and closely inspect the various brake components. Inspect the magnet arm for any loose or worn parts. Check the brake shoe return springs, mounting springs, and adjuster spring for deformation. Manually move the actuating arm or lever and check for any binding or rubbing. Replace the magnets if they show signs of uneven wear. Some magnets may have recessed screws; if the wear is down to the screws the magnets should be replaced. In some instances it will be necessary to have the armature plate resurfaced. This cannot be done without a special lathe. Call your local service facility if an armature has developed a pattern of grooves due to worn or damaged magnets. It is wise to replace all the same items of the same axle even if only one side necessitates replacing. If, for instance the right side magnet is worn, but the left side is okay, replace them both. Keep all like components on the same axle, the same age. There are two areas of the brake drum that are subject to wear and require periodic inspection. These two areas are the drum surface where the brake shoes make contact during stopping and the aforementioned armature surface where the magnet contacts. The drum surface should be inspected for excessive wear or heavy scoring. If the wear marks are worn more than .020", or the drum has worn out of round by more than .015", then the drum surface should be turned. If scoring or other wear is greater than .090", the drum must be replaced. To ensure proper contact between the armature face and the magnet face, the magnets should be replaced whenever the armature place is resurfaced. Unlike most automotive brakes which are self-adjusting, electric brakes require periodic adjustment to keep the shoes properly spaced. Here is the procedure: jack up and properly support the trailer so that the weight is off the wheel and remove the plug from the back side of the backing plate so that an adjusting tool can be inserted through the hole. Slip the tool tip into a notch in the star wheel and ratchet and rotate the star wheel to expand the shoes against the drum (rotation may be clockwise or counter-clockwise, depending on the brake manufacturer). Expand the shoes until you cannot rotate the tire any further. This centers or seats each shoe evenly against the surface of the drum. Then back the adjustment off in the opposite direction until the wheel turns freely but has a very slight drag while rotating the tire by hand. Replace the plug to keep dirt and moisture out. Repeat this process on all brakes. If all the components appear to be in working order and nothing appears to be bent or damaged, at the very least, replace all the springs in all four brake assemblies. But it's my guess you'll find a broken spring or a damaged or bent component somewhere in there.
Dear RV Doctor, what does DSI stand for as in a water heater with DSI? Sheri Yeakle, ( Spencer , TN )
Sheri, DSI stands for Direct Spark Ignition. That means it's an automatically lit water heater. There is no pilot flame. You activate (and light) the burner by turning on the switch inside the RV. When the water reaches the set temperature, the burner goes out. As you use the heated water, the temperature inside the water heater drops as cold water enters. The DSI circuit board will then open the gas valve, create a spark and light the main burner flame again, heating that tank of water. It will also close the gas valve in case the burner goes out for any reason. Besides being utilitarian, it's also a safety device. It sure beats having to go outside and light the pilot flame at the water heater, hoping it stays lit..and does not blow out in the middle of the night. Thanks to the innovative Fenwal Company and the forward thinking staff at Suburban for engineering one of the best inventions ever for the RV industry!
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