Did it quit with a smell of ammonia in the outer refrigerator locker, and possibly some yellow stains on/near the tubes back there? If so, it needs a new cooling unit. These are available, but there's some disagreement on whether or not it's worth the cost and effort. I list that as the most likely option, since if it's the original '71 unit, if it cools on both gas and electric one day, and won't cool on either heat source the next, it's probably the absorption unit. If you're living in it parked in a fixed location, the cheapest solution is an electric-only "dorm fridge" that fits in the space. New RV fridges are on the high side of $1k.
Il Carriaggio — 1975 Argosy 24 | Il Progetto — 1976 Argosy 28 Center Bath | WBCCI# 15566
He has all of the virtues I dislike and none of the vices I admire. — Sir Winston Churchill