Electric Fan Wiring

[SantaCruz163]

I searched and found a few threads on the topic of swapping to an electric fan. But I couldn't find a thread that gave the wiring schematics to wire the fan. The popular choice seems to be running the low speed fan to the thermostat (I assume this turns the fan on with teh stat opens?) and then run the high speed to a manual switch inside the cab.

 

I would like to wire this properly so I don't burn my rig down.

Edited July 14, 2007 by SantaCruz163

[nissandoms47]

The thermostat is all mechanical. When it reaches a certain temp it opens.

[SantaCruz163]

Well, I read that the low speed fan is ran to something in the fuse box, to basically turn on the low speed at a certain temp. Then, a manual high speed. Is there a wiring schematic somewhere????

[nissandoms47]

It depends on what kind of fan you're going to get. What people usually do is go to autozone and buy a tempurature sensor relay and it has a little probe that you stick into the fins on the rad and when it reaches a certain temp it turns the fans on. I would just wire it so that it always turns to the high setting. Thats how mine are.

[jj big shoe]

Below is how I wired my Taurus fan, low speed only.

You'll need a large relay (I used an 80 amp), some 14g wire, some 10g wire and either a t'stat wiring kit or a standard automotive single pole double throw (SPDT) relay. The smaller relay will trigger the large relay, which throws power to the fan.

 

Run 12v to the fan t'stat (use a 12v source that is switched by your ignition or the fan will still be running when the truck is turned off).

Run the other wire coming from the t'stat to #85 of the small relay (splice into the 12v line that turns your AC compressor on and connect it to this wire and your fan will come on whenever the AC is on. It'll make your AC work much better).

Run a 14g wire from #30 of the small relay to the pos. battery terminal.

Run a 14g wire from #87 of the small relay to #85 of the large relay (you prolly don't need one, but I added a 25a inline fuse).

Run a 14g ground wire to #86 of the small relay.

Run a 10g wire from #30 of the large relay to the pos. battery terminal.

Run a 10g wire from #87 of the large relay to the fan's pos. lead.

Run a 14g wire from #86 of the large relay to the neg. battery post.

Run a 10g wire from the neg. battery post to the fan's neg. lead.

 

Splice a 1000v 3a diode (1N5408) between the pos. and neg. fan leads as shown, paying attention to the polarity of the diode. Electric motors create current when free spinning and this diode will bleed voltage off down the ground wire so it won't damage the relay.

 

The switch shown is to disable the circuit for water crossings. High speed fan blades tend to warp and deflect when they hit water and could rip into the radiator, so I wanted to be able to shut it off.

 

For a switched high speed option, you'll need another large relay wired the same way, except run your 12v wire with the switch to #85 of the second relay and hook the high speed lead from the fan to #87 of the second relay.

 

I used an adjustable t'stat and dropped the temp probe into the upper radiator hose instead of between the radiator fins. Works fine if you wrap some electrical tape around the radiator tube to take up the gap the probe wire will make between the tube and the hose.

 

Umm...I think that's it.

Edited July 15, 2007 by jj big shoe

[zonianbrat]

I am going to have to bribe someone with beer to come to my house and help me out with this. I hate wiriing things up, I always do something wrong or backwards, and when it comes to cooling my engine I want it done right. I have a taurus fan sitting in my garage.

[88pathoffroad]

Buy a thermostat kit and follow the instructions. It's really not that hard.

[zonianbrat]

I do plan on buying a thermostat kit 88. It is always funner to have someone else there drinking beer with ya though!! Got any idea how much one costs? guess I could just go online to Vato-zone and find out. Are the kit's generic to most vehicles or do I need a certain one?

[jj big shoe]

Nah, the kits are generic and cost about $45 for one with a static t'stat. An adjustable kit is about $80-$120. I used a wiring kit and half way through the install it dawned on me that it's just a standard SPDT relay and some wires with spade connectors crimped on already. I later found an adjustable t'stat at Napa and swapped the static one out. A SPDT relay and all the wiring and connectors you'd get in the wiring kit costs about $12. If you could find an adjustable t'stat to buy by itself I'd go that route. It really just looks more complicated that it actually is.