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Thursday, May 26, 2011

RV Refrigerator "Auto Mode" Problem

I recently purchased a Coachman Class A motorhome with a Dometic refrigerator Model RM2852 that has an "Auto Mode" switch to start up electrically using 120-volts alternating current. 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 only use the "Gas Mode" switch to start the refrigerator. It will not start using the "Auto Mode". The light inside will come on so it is getting power but it will not get cold even after 24 hours. Can you advise what is causing this problem? Patrick H., (Hockessin, DE)

Patrick, 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, both the “Auto” and “AC” lamps should light up. If not, there may be a blown fuse on the lower circuit board. It’s relatively easy to check if you have a volt, ohm multimeter. It’s possible you may have a problem with other components or wiring within the AC circuitry, but the most common cause is a blown AC fuse on the lower circuit board. But when it’s 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. Then carefully remove the cover. Once removed, plug the refrigerator back in, power the RV with 120-volts AC and set the refrigerator to the “Auto Mode.” Next 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 be able to measure 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 realize that if the serial number of your refrigerator is between 101XXXXX through 152XXXXX, it is subject to a recall notice. Ensure your unit has been retrofitted with the recall kit. 


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