Foul Battery Odors
Dear RV Doctor:
On a recent camping trip, our motorhome was connected to 30-amp shore power. During the night, our carbon monoxide (CO) alarm went off. Since there was no stove or furnace operating, I concluded the alarm must be defective. I did notice the coach battery compartment was warm to the touch. Later, when entering the motorhome from outside, I noticed a foul odor that I couldn’t identify. We drove the motorhome back to Cincinnati, Ohio, and I hooked it up to shore power (30-amp). This morning I went to the RV, and the CO detectors (two of them) were going off. I opened the battery compartment and found the batteries and cables to be very warm, and I noticed the same foul odor. Is it possible that the batteries are producing carbon monoxide?
Fred Newman, F235091, Cincinnati, Ohio
The charging and discharging of batteries will not produce carbon monoxide. But unless they are charged properly, they will off-gas a foul odor that consists of hydrogen vapors and sulfuric acid. Rapid charging or rapid discharging of the batteries also will produce an abnormal amount of heat. I’m not sure what brand of CO detectors you have, but it may be that they are sensitive to the boiling of the electrolyte that probably is taking place.
Without being able to run tests and take measurements on your battery system, I’d hazard a guess that the AC-DC convertor is overcharging the battery bank every time you are plugged into shore power. Be sure to keep a close eye on the electrolyte level in each battery in that bank until you rectify the problem. Overcharging can literally boil the water right out of the electrolyte; produce heat; and off-gas the hydrogen and sulfuric acid. This is the odor I believe you smelled. The foul smell also could indicate that one or more cells in the battery are bad, causing the convertor to overcharge the batteries.
In my opinion, many stock charging convertors are not sophisticated enough or engineered with circuitry designed for the complete and proper charging sequences necessary for optimal battery charging. Many have a propensity to overcharge the battery bank. I’ve always suggested investing in a three-step or four-step battery charger. That way you can allow the convertor to convert, and let the battery charger do the charging. Multi-stage, processor-controlled chargers can be set to accommodate any type of battery so it knows how to charge, when to charge, and at the proper current and voltage so that overcharging cannot happen.
Refrigerator Ice
Dear RV Doctor:
We are new full-timers, and I’ve noticed that the fins inside our Norcold refrigerator are icing up. What causes this? Is this normal? Should I ask how to prevent this?
Casey Dossey, St. Louis, Missouri
Some ice buildup on these fins is normal. However, if the refrigerator requires defrosting more often than the freezer, you do have a problem. (It is recommended that the freezer be defrosted when the ice reaches 1/4-inch thick.)
Severe icing can be caused by a number of circumstances. First, you may be setting the temperature too low. Also, check to make sure that the restrictor is in place in the condensate drain. If this is missing, warm, moist air can enter the refrigerator and lead to excessive icing.
Depending on the model, the refrigerator’s thermistor may be out of position. This is the device used to determine the cold setting on the thermostat. Or, the refrigerator may have a faulty door gasket leaking air.
After checking the temperature setting and assuring that the restrictor is in place, you should perform what we call the dollar bill test. Close the lower refrigerator door(s) onto a dollar bill at various points around the entire seal. With the dollar bill being held in place by the door seal, try to pull it out. You should feel a slight drag or resistance on the bill as you pull. If it just falls out or you feel no tug, chances are the gasket is faulty and needs to be replaced. Be sure to do this at multiple positions around the entire seal of each door.
If your refrigerator passes the dollar bill test, then send me the model number and I’ll look up the exact positioning of the thermistor on those fins. You also should be sure to have plenty of room for air to move about inside the cabinet section. Avoid using wide trays that may block some of the convection movement inside the box. This, too, could cause icing on those secondary evaporator fins.
Air-Conditioner Freeze
Dear RV Doctor:
We have a 15,000-Btu, roof-mounted, ducted Duo-Therm air conditioner on our motorhome. Here in Texas, with temperatures above 100 degrees during the summer, our air-conditioning unit kept freezing up, leaving us without cooling for more than an hour while it thawed. It puts out good cold air, but it will freeze up at least twice daily, sometimes even in the middle of the night when the sun is down. This will happen whether we are parked in the shade or sun. We have tried not using the ceiling fan, which is right in front of the return. We have tried directing the air through the unit’s shutter vent instead of sending it through the entire coach via the ductwork. Much to our dismay, nothing seems to work. Any suggestions as to what we can do to prevent this?
Liz Stafford, Sunnyvale, Texas
Ice can form on the air conditioner’s evaporator for a number of reasons. One of the most common and easiest to remedy is poor air circulation caused by a dirty filter. The air conditioner must have adequate air circulation to work properly. If you haven’t cleaned the filter recently, do so. If you use the air conditioner often “” as it appears you do “” clean the filter on a regular basis. If it looks dirty, clean it. Ice also can form as a result of the fan being set at a low speed; high humidity; or an unrealistically low temperature setting.
All Duo-Therm roof units have a freeze-control device specifically mounted on the evaporator coils. The positioning of the control switch is crucial to proper operation. Have someone check to see whether the control switch is in the right position and that it indeed measures no continuity when the ambient temperature is above 69 degrees Fahrenheit. It’s entirely possible that the switch has come loose from its mounting or is faulty. This freeze control is a thermally activated switch that closes once the temperature of the evaporator falls below 49 degrees. Once closed, it will reopen when the temperature rises to between 61 and 69 degrees. If it fails to open and the temperature is above 69 degrees, it needs to be replaced. A simple continuity test and temperature measurement should quickly reveal the status of your freeze-control device.
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