There's one nasty symptom, even if all the bells and whistles see, OK. It happened to us two days before a 3-week trip last season.
Even with all the lights showing things were fine, the fridge wouldn't get cold. I found a thread on one of the three RV newsgroups I visit regularly (can't remember if it was this one) that said "Go look round the base of the fridge's chimney/flue. If there's any yellow powder (powdered sulfur), the cooling unit is dead."
Sure enough, a couple of tablespoons full! We went on the trip, relying on picnic coolers and bags of ice. We must have stopped at every Fred Meyer store on the Oregon Coast, topping up the coolers with ice.
Instead of our planned 3 week trip, we bagged it after two and headed home. $1800 later we had a new fridge installed. We decided that going with a residential fridge would have probably discouraged potential buyers, as we expect to give up the RV life this year due to cost.
Frank and Eileen
No longer RVers or FR owners