Frozen Holding Tanks
Dear RV Doctor:
I think I really messed up. Last night the temperature dropped to minus 5 degrees. I thought about the fresh water and left it dripping at a faucet, but I never thought about the black and gray holding tanks. They were left closed, and by the time I thought about it at 2:00 a.m., it was too late. What is the best way to get them thawed out? The temperature is supposed to stay below freezing for a couple of days. Thanks!
John R., Elko, Nevada
If your holding tanks are not in a heated compartment but are protected by a subfloor or an enclosure on the bottom of the motorhome, a droplight with a 100-watt lightbulb placed within the same void eventually will thaw the contents of the tanks, albeit somewhat slowly. If the tanks are exposed underneath the motorhome, a hair dryer or, better yet, a heat gun, can be used to gradually thaw the tanks. But be extremely careful to not allow the heat gun to stay focused on one portion of the tank for too long; it can easily melt the plastic container. Moving the heat gun over the bottom of the tanks in a slow arc will eventually deice them. It may take a while, depending on how large the tanks are, but the contents eventually will thaw. Be very sure the tanks are completely thawed prior to operating the waste valves for evacuation. It’s okay to also use the heat gun on the valves; just don’t linger too long in one spot.
In the future, you can always add windshield washer fluid (if permissible in the sewer system in your area) or RV antifreeze to each tank to keep them from freezing. Also, the fuller the tanks, the less likely they will be to freeze. Just keep adding a half-gallon of antifreeze each day the temps remain below freezing.
Non-Automatic Auto Mode
Dear RV Doctor:
I recently purchased a 2006 Coachmen Aurora Type A motorhome with a Dometic refrigerator (model RM2852) that has an “Auto Mode” switch to start the refrigerator using 120 volts AC. It also has a “Gas Mode” switch to start up by using propane. After several successful trips using both options, a problem has developed where I can use only the “Gas Mode” switch to start the refrigerator. It will not start using the “Auto Mode.” The light inside will come on, so I know it’s getting power, but it will not get cold even after 24 hours. Can you advise what is causing this problem?
Patrick Harty, F415397, Hockessin, Delaware
You say you can run the refrigerator on “Gas Mode,” but when you switch it to “Auto Mode,” does any indicator lamp illuminate on the control panel? When on “Auto” and the coach is energized with 120 volts AC, the “Auto” and “AC” lamps should light up. If not, you may have a blown fuse on the lower circuit board. It’s relatively easy to check if you have a multimeter. It’s possible you may have a problem with any number of the components or wiring within the AC circuitry, but the most common cause is a blown AC fuse on the lower circuit board. But when the refrigerator is running on “Auto Mode,” that indicator lamp should remain lit.
Here’s what you can do: Unplug the refrigerator from the receptacle and gain access to the lower circuit board at the rear of the refrigerator. Carefully remove the cover. Once removed, plug the refrigerator back in, turn it on “Auto Mode,” and measure for AC voltage at terminals J5 and J6 on the board itself. If the unit is already cold, you may have to turn the thermostat to a lower temperature setting or wait until it warms a bit. You should also read the line voltage on terminals J7 and J8, as they lead directly to the AC heating element. If you don’t have voltage at these terminals, check for continuity of the 5-amp AC fuse and the 3-amp DC fuse on the board. Chances are the 3-amp DC fuse is good, since the DC lamp works inside the refrigerator, but I’m guessing the 5-amp AC fuse is blown. A worst-case scenario is that the board itself is faulty. If indeed you can measure line voltage at terminals J7 and J8, then it’s possible you have a burned-out heating element. If that is the case, I’d recommend a pro service tech do the replacement.
Also note that your refrigerator is likely subject to one of two NHTSA recalls (06E076000 and 08E032000) that involved Dometic refrigerators manufactured from April 1, 1997, through September 30, 2006. Ensure your unit has been retrofitted with the recall kit.
More Battery Power?
Dear RV Doctor:
I have two house batteries in my motorhome. They are Interstate SRM 24 RV/marine deep-cycle batteries. I want to know if I can upgrade to the next size for more capacity, or should I just stay with what I have? I do very little dry camping, but it’s always nice to have a larger capacity when it is needed.
Bob Hubert, North Huntington, Pennsylvania
My philosophy has always been that you can’t have too much battery storage capacity as long as you have the means necessary to keep a larger bank charged. I recommend carrying as many batteries as your wallet can endure as long as you have the physical space to put them. The key is having the correct battery charging capability to keep a larger bank charged when connected to shore power. A minor step up for you would be to go to Group 27 batteries, but you will need to determine whether the longer Group 27 batteries will fit in the space used to hold the Group 24s.
You also may consider going to AGM batteries or true deep-cycle batteries in order to gain additional capacity. Just remember, if you add more storage capacity, you also will need to have a means to adequately charge those batteries.
Given that you do little dry camping, I think your idea of going to Group 27 batteries will yield a few more amps of DC power and likely will allow you to keep your current charging system. It will take a little longer to charge the Group 27s, but you probably won’t have to upgrade the charger or the cables if they are sized correctly now. A solar charger is always another viable option should you need more boost in the charging category.