Mazak VTC 20B - Overheat

Our VTC decided not to start up this morning. The control comes to life but there is a 219 alarm - "Main transformer overheat" This apparently happens when a temperature exceeds 120° C. The machine has been cold all weekend and is still cold this morning. I know there is a temperature sensor in the transformer box. Should this be normally open or closed. I have tried disconnecting the feeds to see if I can trick it into starting up but no luck. Does any one know if there is another sensor I should be looking at?

Thanks

Will