I installed 4-90mm Surplus Computer Fans that I bought for couple of bucks each at a Computer Repair Shop!
Mounted them side by side on a piece of scrap aluminum angle that I had left over from another project. This got bolted to the top of the Fridge exhaust Vent stack below the plastic Cover.
The Wire feeds down the back of the fridge and connects to the 12 Volt Power supply. It is fused and has a switch which I located in the cupboard above the Stove which is beside the fridge.
I thought about adding a thermal switch or using a speed control but haven't gotten around to it .
The Fans are just barely audible while running,draw very little power ,so are usually on 24/7 .
We have Several Solar Panels on the Roof which help maintain the Batteries.
Rob & Jean
98 Dutch Star Diesel Pusher ..07 Honda CRV AWD