Why is the fan of the Torpedo Captor (or Captor X) not (or barely) turning ?

The fan of the Torpedo Captor and Torpedo Captor X is powered by the signal coming from the amp itself. It does not require the phantom or external power supply. This means you can use your Torpedo Captor/Torpedo Captor X as a loadbox or an attenuator without needing a power supply.

This also means that there is no active circuit controling the speed of the fan. Its speed is simply proportional to the power coming from the amp. The fan only begins to turn when the signal from the amp is powerful enough to make the Captor/Captor X heat up, and the more power coming from the amp, the faster it turns.

If you play your amp low, or use a low wattage amp, the fan may not turn at all, or will only turn slowly. This is not a malfunction. If you play a high wattage amp loud enough, the fan will turn very fast.

Finally, the fan only turns when you play, and stops when you stop playing. If you play for a few second then stop, the fan will do the same: it will turn for a few seconds, then stop.