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RV Doctor ColumnRV Doctor #328 Dear RV Doctor, the right front brake on my travel trailer 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. Don Lewis, (Downer's Grove, IL)
Don, it is quite possible there is a mechanical problem with some of the components in that 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 and check for any binding or rubbing. Replace the magnets if they show signs of uneven wear. Though not all wheel assemblies have a replaceable armature, it may be necessary in some instances to have that plate resurfaced. This cannot be done without a special lathe. Call your local service facility if the armature has developed a pattern of grooves due to worn or damaged magnets. In newer drum assemblies it will be necessary to replace the complete unit. 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 inches or the drum has worn out of round by more than .015 inches, then the drum surface should be turned. If the scoring is greater than .090 inches, 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 inside the drum. 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. Engage the star wheel and rotate the it 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 at all. This centers or seats each shoe evenly against the surface of the drum. Then back the adjustment off in the opposite direction until the tire turns freely yet has a very slight drag while rotating it by hand. Repeat this process on each brake. 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 Gary, we have a Dometic refrigerator in our RV with a strong smell of ammonia inside and outside of unit. Plus the refrigerator won't cool at all. The motorhome has been parked level for the past few months. This was our first usage this season. What gives? Jim Mondt, (Auburn, WA)
Jim, unfortunately, you have a leaking cooling unit which renders the refrigerator inoperable. The entire cooling unit will have to be replaced. Not an uncommon occurrence, cooling cores can develop leaks due to moisture entrapment within the foam insulating block. A rupture or crack in the tubing results in the release of the ammonia. If the leak point is situated at or near an exposed section of tubing at the rear of the refrigerator, a bright yellow residue is usually visible. If the leak is in a section of tube hidden by the foam block you may not visibly see it, but any indication of an ammonia smell confirms a leak indeed. Typically, service centers replace the cooling core with a new or refurbished unit, sending the damaged core back to the supplier to be repaired, recharged and placed back into inventory. The entire replacement can take anywhere from two to four hours to complete. Cooling units cannot be repaired in the field - they must be replaced. Not an inexpensive venture, oftentimes RV owners must contemplate a complete refrigerator upgrade versus just the cooling unit replacement. It depends on the age of the refrigerator and how fond you are of your existing unit. On units around eight years or older, seriously consider a complete refrigerator replacement. A new refrigerator will have a new warranty and all new parts. With a cooling unit replacement only, the remaining original components are still aged and non-warrantable. Your local Camping World store will be able to accommodate either choice you make.
Dear RV Doc, my Emerald (6500-watts) generator has 1220 hours on it and is putting out 160-volts. It has never been decarboned but has had several doses of Onan 4-C. It seems to run okay other than the over-voltage. It ran sporadically at 120-volts but was able to run two air conditioners but now, every time, it ramps up the output to over 160-volts. Any advice will be appreciated. David Guttas, (Livingston, TX)
David, do not allow the generator to power any device in the RV while it is putting out 160-volts AC. It will most assuredly damage the roof air conditioner and all other devices designed for 120-volt AC output at 60-Hertz. Obviously, the governor, which controls the speed on the generator, is out of adjustment. The generator speed affects the frequency (Hertz) and coupled with the carburetor, affects the output voltage as well. Generator carburetors and governors require a certain amount of expertise to get into synch. It's vital to understand that RV generators cannot be tuned by ear. It takes a special piece of equipment called a load bank to correctly tune and set-up an RV generator. Keep in mind that the carburetor adjustments and the governor adjustments, though mechanical in nature, will always have an electrical result or consequence. The load bank must be attached to the output of the generator to safely and correctly monitor the voltage, load and frequency while making any adjustment. Full service RV repair facilities will have a load bank on hand for such service. Do not attempt to do this without one (it appears someone already has). I wish I had better news for you, but I think this one should be left to the pros.
Dear RV Doctor, I just bought a very clean but older Franklin travel trailer. A previous owner, about two years ago, installed a new converter charger, but there is no battery in the system at this time. I want to install a deep cycle battery, but don't know what to look for as far as the wiring goes, so the battery will be charged. Al Bauer, (Summerdale, AL)
Al, all converter/chargers will have a separate output for battery charging. If the new converter is indeed a "charging" converter, look for battery connection terminals. If, however, it is not a charging converter, the output wires of the converter are simply wired directly to the fuse panel for all the DC circuitry as well as a parallel connection to the battery. Most modern day RV converters are indeed charging converters, though the highly sophisticated ones with three or four-stage charging are the better chargers. Some RV converters are simply mediocre battery chargers at best. Let me know the brand and model number and I'll see if I have some further info for you. But if it is indeed approved for RV use, it quite possibly will have battery connections on it somewhere. Both the hot and the ground from the battery should be wired to the converter.
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