This is from an earlier thread.
Re: Dometic RM1350Yours is like mine, in a slide. You do not have a top vent out of the coach. There are two vents on the back of the refer., outside. This setup does not allow hot air to escape as easily as the rooftop style. IMHO
Have someone pull the top vent cover off. Mine only had about 2'' of air space above a sheet metal flange that was blocking 3/4 of the opening on the back of the fridge. Apparently this directs the air up and out for a roof vent, but it doesn't work so well for the back vent style, such as we have.
The dealers' tech cut about 3 to 4 inches off of this sheet metal flange going across horizontaly to allow more hot air to flow out at the top. This seems to have done the trick, as mine seems to be staying quite a bit cooler for now. He said that another 3 or 4 inches could be cut off, if necessary, but It doesn't seem to be needed at this point.
Good luck, Trace