Just looking at the operation of it, there is a 12v supply to the relay and the thermal switch, it has two modes so the hot running will kick in after the cold running. Say the cold running is selected, with the thermal switch made, the 12v will then be made to user selector switch at position R2, switched to cold this will then put a 12v through S1 to the East position of the relay. I'm guessing this will be the solenoid supply to make the relay close between the N and S postion. This will then allow the permanent 12v from the North position to activate the fan from the S position of the relay.
Hope this helps your fault diagnosis a little, correct me anyone if I'm wrong, may be a duff info.
