Flyback diode selection

What are people using for flyback diodes on things such as thermofans. I'm not completely sure how to best select one, is it just a case of picking something with a sufficient amperage rating.

Good question, I'm not sure how/if this has been addressed in the guides, but I would suggest yes - the trick is knowing what that's going to be.

You'd need to select a diode that is rated to at least the current draw of the fan which should be provided by the manufacturer. Diodes also have a voltage rating which unsurprisingly needs to be able to handle the voltage of the system which is of course 14 volts. In this case a safety factor of 2 would be typical so something rated above 24 volts should suffice. The above would be suitable for a on/off operation but if you're planning to use PWM speed control then things can become much more complicated.