Been doing some research on how to better use a taurus fan and BMW uses a dual temp fan switch part # 61318361787 made by facet on the 1995-1997 Z3. It is a metric thread but there is a guy on ebay that makes a brass threaded sleeve that allows it to be used in a GM car. Another guy on ebay has one of those water necks with the two threaded holes and he has two individual temp switches in it but it is FUGLY and looks like it came off of a 1986 truck or something. The dual fan switch needs to be from 80C to 88C which works out from 177 Degrees to 190 Degrees Fahrenheit. If someone has more expertise in this area please chime in since I am just investigating
(learning) this. I will post later with more info since the taurus fan and markVIII are the best fans out there and I would like to start using both speeds on my taurus fan.
hollisterroadco on ebay offers the BMW dual temp switch with pigtail and brass sleeve for $76.00 for the two speed fans. He also has relays for the fans also.