Hygena APM 6214 Intergrated Freezer.

I hope someone can guide this silver surfer. We came home to find the red light on and it had started to de-frost, I turned up the stat but nothing so I turned the freezer off for a couple of minutes, when switched on again it ran for a few seconds then off, it did this every time.

I ran a meter across all the teminals like brown and black and white and black, then brown and black again, each test caused the meter to screach aloud so my limited understanding told me the stat was OK but I am not sure as the stat has a Brown, a Blue, a White, and a black and lastly an earth wire so I don’t really know if it’s a thermostat problem or a compressor problem. Can any kind person advise me how I may check this fault. Of course the freezer was disconected from the mains. Many thanks in advance.