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Electric Fan Wiring

16960 Views 22 Replies 11 Participants Last post by  ScreaminZ
I couldn't find much when I went to install my flex-a-lite fan. It came with an adjustable thermostat - not the control box most people use. This setup has a switched override for when the A/C is running and is only powered when a switched ignition source is powered. I did not include a manual override to turn it off, but you would just need to cut the ground to the fan. Other write-ups on this site show how to wire in the A/C relay should you choose to do so. Also, this is a puller setup. Hopefully this helps someone.

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Looks good
Only thing I would do differently is put the fuse before the relay. With power and ground wires going to the relay, its possible to have a short internally. If that happened without a fuse the weakest wire is going to burn.
Good idea, thanks for the help with my other posts BTW.
ok i dont know much with electric, but

with a circuit the power has to flow both directions correct? so is a temperature switch capable of handling all of the electric fan's power going through it? isnt it like hooking up a 1000 watt audio amp with a huge power wire and a tiny ground wire, so the circuit can really only flow what the tiny ground wire is capable of? i was going to do the diagram above but will most likely do this instead>

kaised im not looking to discredit you im just looking for answers. id rather do the wiring the way it is in your diagram but just wanna double check.
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That diagram in post #1 is VERY dangerous. :rolleyes: Everything about it is wrong. :shrug The fuse is on the wrong side of the relay, and so is the t-stat. The switch isn't even shown correctly - it'll catch fire, the way it's shown. I'm not trying to hammer you, but I don't want anyone to build that circuit.

The top of the diagram in post #4 is better, but it doesn't show any fuses, and doesn't have any driver input, which IMO is the only reason for using an electric fan. I want to be able to turn it off before deep fording, or force it on if the temperature switch fails. The bottom one seems kinda pointless - it has no temperature control, and the only function of that switch is to make the fan run continuously with the key off, which could kill the battery.

This is the circuit I'm building for my truck:

I haven't decided where to put the temperature switches, but I might re-build this with more ports:


Here's a simpler version.

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i think electric fans are the way to go i think they give you about 16% more HP. would any body suggest any old fan that is the right size with the proper wiring and mounts?? looking for a low-buck solution.
order a mark 8 fan from steve83. click his sig there he has some then you will have to shoot him an email. all you will need is a controller of some sort to run it.
Another alternative is Ford 3.8 Taurus or Windstar fans. I have a dual fan setup out of a Chrysler LH sedan in my truck adn it works well...:rockon
I was gonna put a Mk.VIII fan into my truck (just because I HAVE them, and I didn't want to buy a new clutch), but it wouldn't fit. :madder

Fortunately, I had a pair of fans from SOMETHING else :scratchhe that just needed a new resistor (which I found in the JY :D). So I bent a frame from 1/2" EMT & mounted them up. They worked fine yesterday off-roading all day, and I only had them wired to run in low speed continuously. No pics of them yet - I was in a hurry.
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same here with the clutch, im afriad that the fan will go into the radiator some morning like it did in a friend of mines F-150.
looking at it the mark fan should fit with my 302
V8s are 2 cylinders (~9") shorter than I6s, so yes: it'll fit fine. But if you check the clutch more than 2x/yr, you'll have plenty of warning before it breaks loose.

i think electric fans ... give you about 16% more HP.
alright the hp increase was sumthing i saw on the history channel, ok thats why i said I THINK. it does take a good bit of strain off the engine though. and im defintly sure that the fan clutch is shot and im replacing it next week.
it does take a good bit of strain off the engine though.
:bs The energy to move the air STILL comes from the engine. But with an e-fan, that energy has to go from being kinetic (mechanical), to electrical (thru the alt), then it has to flow thru several wires, contacts, & connections, & then get converted BACK to kinetic (fan motor) before it can be transferred to the air (fan blades). So all that loss has to be compensated for by pulling MORE power off the belt.

With a clutch fan, the energy transfer is directly from the belt to the blades, which is more efficient.
Steve you cant trim the shorud of the mark 8 fan a bit to get it to fit?
hmm looks like in the pics if you cut about 1/2 inch off shroud/housing it would fit.
I run the Mark 8 fan in my 85 its great I bypassed the thermostat and ran just switch one the dash one of the easiest installs. If you go to pepboys you can get a generic electric fan relay and wiring it was like $20.
...if you cut about 1/2 inch off shroud/housing...
The fan would hit the radiator before the motor got far enough away from the WP pulley.
I fit a MarkVIII fan on my truck by cutting the shroud.

But I have a 460 so maybe its shorter.
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...I have a 460 so maybe its shorter.
Yes, an engine that has 4 4" cylinders in a row (or 2 rows) is shorter than one that has 6 4" cylinders in a row. ;)
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