I'm looking to wire a manual switch for my fan, and came across a lot of threads asking for a diagram on how to do this. Here is a pretty straightforward set of instructions and a diagram.
It is the diagram from SPAL Fans for wiring a single fan. It looks like SPAL provides a new relay, so people looking to do this will have to find out what color their OEM relay wires are and make corrections accordingly.
Just putting it out there.