Blocking the Fridge Screen

"a system that already doesn't work all that well on 12 volt."

If yours does not work properly on 12 V then fix the problem. The four that I have run on 12 V have been OK. You just need to replace the wiring with cable that conforms to the Dometic specifications.

So are you saying that your fridges are as effective on 12 volts as they are on gas or 240 volt? I think not. They work, and will keep the fridge cold but they are:

"a system that already doesn't work all that well on 12 volt."

Extract from the Thetford 3 Way Fridge Manual, I guess they'd know?

"DC operation guidelines:
DC operation is intended only to maintain the temperature of the
refrigerator and its contents when they are already cool.

The DC operation is not intended for the initial start up and
cooling of the refrigerator. Always use either the AC operation
or propane gas operation to initially start up and cool the
refrigerator.

The refrigerator must be cooled and the temperature
must be steady before you operate the refrigerator on DC."

Notso, the later model Dometic fridges have the same size element on 12 V as they have on 240 V. They are capable of the same performance on 12 as they are on 240 V. The earlier ones do not have thermostats in the 12 V line so the element power is reduced a bit to stop them freezing the contents when the wiring to the fridge is of the proper size. Those who continue to say that the Dometic fridges are no good on 12 V are those who have them and refuse to or don't know they should upgrade the cables all the way from the alternator to the fridge.

Two things, the original post says nothing about the fridge being a "Later Model Dometic", and when you say they have the same size, I seem to recall reading the dometic specs a while back that basically says the 12 volt has 170 wats and the 240 has 180, so it is a little less. There is one other aspect and in the ideal world where caravan manufacturers do put in decent wiring then a 12 volt will work reasonably well, but as we all know the world is not perfect and many installations are less than ideal. A small amount of resistance in connections and attenuation over distance can make a huge difference in the 12 volt system.

Why block it off? In over 200,000 km of travelling I have not had much dust enter the fridge cavity. If you are getting dust into the van through there then fix that problem, it means that the fridge cavity is not sealed from the van interior like it should be.

If you block the bottom vent you are likely have the working parts of the fridge overheat if it is run with the cover on. You never know what helpful assistqant will start it up without removing the cover.

Thanks for posting that Peter. My thoughts exactly but I was a bit slow in posting such.
If a cavity is sealed there won't be much dust entering. There really needs to be a flow of air containing dust for dust to accumulate in a cavity.

I have travelled a lot of dusty roads. There is only a couple of millimetres of dust on the floor of the cavity. I consider it is not sufficient to worry about. The fins on the back of the fridge are fairly clean and it works efficiently in hot temperatures.. As I said above, if you are getting any dust from the fridge cavity into the van then the fridge is not installed according to the regulations and you should have it attended to.

I think it is also a legal requirement to have an open vent in a van behind the 3 way fridge so if your van happens to catch fire and the vent is found to be blocked it may create so extra problems just for the sake of trying to eliminate dust that may not even get in. So blocking it off with something like foam as I mentioned that can still breath or fitting exhaust fans will be a safer option than blocking it off with say cardboard or a piece of ply or similar.