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Electric fan conversion 1985


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I have a 1985 720 king cab.  I jus but and have to replace the carb so I figured let's do an electric fan conversion as well.  I have the fan mounted a 12 fan. Will add another one soon.  I have it all wired but the AC turn on wire

   I can not find where the wire or a place to tap in to the AC.  Would it be best to just run that to the fuse panel on the inside?  Any help would be nice thanks in advance.  

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What I did was run a 12 gauge power wire directly from the battery through a 50 amp fuse to a relay beside the rad and from there to the fans and to ground. The relay is turned on by an in line temperature sensing switch located in the lower rad return line. I think it's set for about 185-190F. In the lower rad line it turns on the least amount of times than on the rad, or worst of all the top rad hose. It will also come on and cool during heat soak times just after the ignition is turned off on really hot days. This prevents any chance of boiling and the expulsion of coolant out the overflow tube. The relay is essential to making this totally automatic and removes complexity and human error, like forgetting to turn the fans on or off. If planning to run the fans all the time you may as well leave the mechanical fan on there. 


I have two large fans from some Subaru but they won't fit side by side so I reversed wired one and mounted it behind the rad and it pulls air in and the other mounts on the front that overlaps the other and pushes air in. They come on at long stop lights or when idling long enough. Most of the time they are not on at all because vehicle movement pushes air through the rad or the engine is cold and has yet to warm up.

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Mechanical fans usually pull more CFM than the commonly available electric fans, so I don't love replacing mechanical fans with electrical, but you're talking about adding a fan for A/C, right? Good idea.


A good quality electric fan (or two) can perform well enough to replace a mechanical clutch fan, but they usually run high amps, like 30 to 50 amps, so be prepared for that. 10 ga primary wire, fused and relayed, should be used for power.


I like to have my electric fans come on when I push the A/C button. This means that the fans are pulling the whole time the A/C is energized. Some will say, as Mike did, that the fans should be wired into a temp switch, but my logic is that if you're in a climate that A/C is really important, it's a great idea to have the under hood temps as low as possible when the A/C is working. I like it that way, and my customers do too.



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