Refrigerator in slide out not cold enough

I have a Norcold refer and it works fairly well. My brother has a Dometic and was just ok until his cooler unit blew up. He replaced it with one of those amish ones, I do not remember the name, but since then it works amazingly well. Has never worked that good. This might be a option to consider at less than half the cost of a new refer and fairly easy to do yourself. Just a thought.