David is right, the fan needs to be free to rotate. If seized, it should blow the fuse though.
If they are free, I would be next checking for voltage on the fan connector with a DC voltmeter, while the sensor is disconnected.
Here is a wiring diagram of the circuit on the later TF's.
The wiring diagrams are brilliant compared to some I have seen, very easy to follow and the wires are all colour coded.
Sundance