The thermostat turns on the compressor motor when the fridge is warm & off when it gets cold enough. If you bypass the thermostat it will never turn off & run 24/7 freezing everything you put in it. First decide if the thermostat is faulty. Turn power on at wall & check that compressor starts by listening or putting your hand on it to feel if it is running. If motor shuts off before the fridge gets cold maybe only running for 5 - 10 minutes then the thermostat is faulty. If however the motor runs for a long time ( say 1 hour or more ) and fridge is still not cold then the problem is more likely to be a loss of cooling gas in the pipes.
Lincoln Appliance NZ, October 2009