good post on the schematic, thanks. Spoke with factory, RM2652 are the only models with the rocker switch under the top panel, DM is hardwired as you found.
Found the grnd and removed, looks like cooling nicely, also replaced cooling fan with lower watt fan with 111CFM. The removal of the ground wire disabled the fridge light. Looks like you can disconnect the heater grnd at the light switch just inside the fridge. I'll give that a shot just to see if it works.
Ok, on your light in the fridge you'll have one grnd connection on the rear of the light. Cut the heaver gauge wire that is the heater ground. To be sure, the lighter gauge wire think it is 20awg is the one that is going to ground so that one is what connects the light in the series.
Wireing diagram
Linear Mode
