Just done the headgasket on my 1.4 golf. Now the cooling fan isn't coming on wheen it should so the engine is boiling over. the thermostat seems fine, i've checked the fuse and i can't see any connections i've missed off. What else could be causing this? it worked fine before i removed the head. I'm thinking temp sensor or something. can someone please shed a bit of light on this please. thanks.