The Dometic 2852 refrigerator has a "door warming element" molded into the rear side of the door frame. By design, its purpose is to warm the space on the cabinet where the seal magnetically seats, keeping that area dry to prevent condensation/frost from forming. There is no switch to activate the feature and no way to turn it off. It is connected to 12 VDC at the interior light and is "always on" as long as there is 12 VDC to the refrigerator and the unit is operating. You may have a bad element or it may not be connected behind the interior light. You can check by removing the light to make sure all the connectors are properly attached and plugged in.
Next, wipe off the frost, place a dollar bill in the area of the frost, close the door and pull the dollar out of the space. You should feel resistance from the gasket sealing against the refrigerator wall. There may be a bent/warped door or a "mis-molded" gasket. Check to be sure there is nothing inside the freezer that is binding against the door, causing it to not close completely, possibly it's "overloaded" in that area and not closing completely.
Be aware of how you "graze" in the refrigerator. Many of us open the door, then look over everything, checking to see what we want and taking it out while leaving the door open as we sit things on the counter to return and continue to "graze"... Absorption refrigerators, unlike "home style frost free" refrigerators do not have the capacity to move and dry the air inside the closed space. Essentially, when you open the Dometic door, much of the "dry cold air" falls out the bottom and "warm wet air" rushes in to replace it. All of that "warm wet air" will bring frost with it, and the longer the door is open, the more moisture collects on the cooler contents of the refrigerator. The problem is even more of an issue with the frozen contents of the freezer. We've learned to plan what we want from the refrigerator, open the door and get those items "with purpose" and close the door as soon as possible. We no longer graze the trailer refrigerator and we don't leave it open any longer than necessary. That has cut down on the amount of frost accumulation and significantly decreased the frequency of defrosting.
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