Having had the fridge over heating and the sink getting hot earlier in the year I have wanted to fit cooling fans. Now after finding all the right bits they are fitted and working.
I found a small temperature programmer that you can adjust to switch on the fans when the temperature in the top vents get to a set level. The fans then come on until the temperature has dropped four degrees. It is currently set to come on at 40c but I can always adjust this once we get some hot days.
There is a three way rocker, switch fitted above the fridge in the kitchen so that the fans can be switched On, Off, Automatic.