I used to run manual fans too. I'd like to get back to my auto ones working again. I never messed up and left the fans on or anything, but I'm sure it would happen eventually.
Twisted and gchemist, all the sending units I've seen look to be single blade ones like this one from Summit
http://store.summitracing.com/partde...5&autoview=sku
I'm not sure how that would work. I thought the sending unit completed a series circuit which would send power on to the relays to turn the fan on. Am I missing something? The install on those would be a lot cleaner, but I've never seen one with two blades.