The button can be used as a switch.

It just requires you to wire it in that way. The temp sensor tells the ecu to turn on the relay which would all be bypassed if you decide to wire in the AC button as a switch.

The easiest method I found was to use a jumper cable bypassing the AC relay at the fuse box, meaning both fans would come on by the control of the ecu. But I decided to scrap that mod and just run both fans in series. And I've pretty much got them on full time with link.