This is a schematic and parts list to wire up dual electric fans that will only run one fan when AC is on but both fans when engine temp calls for cooling. The temp switch will work with a 180 degree thermostat. If you are running higher temp thermostat you will need to use a different switch.

A 30 amp fuse in the B+ wire will be required. Pick up an inline while at the parts house.

here is a link to the schematic if you want to download it or print it out.
http://farm2.static.flickr.com/1431/537022814_56e7364f85_m.jpg

http://farm2.static.flickr.com/1431/537022814_56e7364f85_m.jpg

30 AMP fuse

you are absolutely right and I did but I made the fatal mistake of ass u me ing that anyone that would tackle the job would fuse it or place a fusible link in the B+ line.
Thanks for pointing it out. I'll fix it.