A few years ago my missus called a bloke out to have a look at our ailing fridge. Very friendly young asian chap turned up. After discussing it for a bit, he said 'is it ok if I give your fridge a bit of a bash?' Having established that he didn't mean anything likely to actually damage it, we said fine, knock yourself out. He wobbled it around a bit, and what do you know, it started working again. He explained that sometimes a bubble gets trapped in the coolant fluid, and stops everything circulating the way it should - dislodge the bubble, and all is well. He said that sometimes with particularly houseproud people he had to kick their fridge after distracting their attention; on one memorable occasion he'd been caught out, and all but thrown off the premises. Refused to take any money - just asked that we keep his card for next time.