Worked through a variety of ways to incorporate fans into the fridge vents to exhaust the hot air for when very hot outside or vents are in the direct sunlight.
Had already bought a controller, 2 fans, fuse and wire so had all the bits.
Initially, built a detachable shade that fixed to the upper vent with in built solar panel generating enough to drive the 2 fans. Though I would fix the fans to the shade and then attach when required. But fixing fans to effectively exhaust hit air was very tricky.
Then decided fans have to fit inside vent and solar feed from the attched shade need to go through vent and be detachable. This prove possible but also could see the vent becoming damaged over time.
The tricky bit for me with fitting the fans etc was where to put the controller with damaging the van and fixing the fans. The connection to the vans 12v was the easy bit as was routing most of the wiring.
Drilled a hole through to the cupboard above he fridge fed the wire though and connected up the controller to the fans, the thermostat and power.
May keep a detachable shade for the upper vent as it does seem effective, when in direct sunlight and will give us a bit more flexibility on parking as we tend to try to park the vent with a bit of shade if possible.
Not sure of the best controller settings yet but upper 36 seems good start. Think it is turned off by default.