All campervan fridges generate heat, both absorption and compressor, and its this heat which keeps the fridges internals cool one way or another.
Absorption fridges are usually vented externally on side vents, and cool air enters at the bottom and escapes at the top, allowing the hot heat exchanger to cool off. Compressor fridges work in a similar way but don’t usually need the vents (as they are only 12v).
The problem is, when its hot, there isn’t always sufficient airflow to keep the fridge cool. We noticed when it was VERY hot and the sun was on the panel of our door, the fridge was less cool.
You can buy thermostatic fan kits for £20-50 – but these are fairly basic and, well, not what I wanted.
So I built my own using some really great, easy and simple stuff.
Simply, its a model W1209 controller, which is 12v, very low power, and controls a relay. You can see the current temperature, and set the switching temp, and you can also set a tolerance level, so if set at 30′ with 2′ tolerance, it will switch on at 30 and off at 28. You can also reverse it so it comes on below a certain temperature. Really quite good! I’ve linked the Amazon UK item – you can get this from China for a lot cheaper.
its a case of using a fan. I’ve gone for the Arctic F12, other sizes are available. These are QUIET PC fans that work straight off 12v and fun fairly quietly. As you can see in my pic I just blow the air on the compressor (which gets hot) and some will go through the heat exchange. I also have a gas drop vent under the compressor and will add a fan under there to “suck air out” – thus when it gets warm, it will blow air over the compressor and expel the warm air underneath.
For an absorption fridge, you’d have the fan(s) blowing air out of the top vent (which would suck cool air in the bottom vent).
You can have as many fans as you want as you just wire it up. The F12 takes 0.3A at full speed, and when its hot we have more solar power than we can store, so hassle free.
Electrically, I’ve just taken +/- from the fridge feed (pre fused), and looped the + to the relay, and the fans are connected to relay and – , so really easy. Yes I need to tidy up the tubing, but its a prototype!!!! 🙂
See http://forum.hobbycomponents.com/viewtopic.php?f=73&t=1900 for details on how to program the unit.