Hi Kay,
If you mean the mesh vents at the back of the fridge, then it's up to you.
You can buy plastic winter covers from a caravan shop - they are the same for every van that uses a Dometic / Electrolux fridge - the primary purpose is to let you use the fridge in the Winter by restricting the amount of air that flows past the fridge and thereby stop the fridge from over-cooling in cold weather. But the covers also prevent rain and crud from blowing through the mesh vents.
If you don't intend to use the caravan from now until next Spring, then you could cover the vents in any way you like - home made covers through to a caravan cover (which covers these vents at the same time as the rest of the van).
Just remember to remove the covers in the Spring.
Robert
