CJ/YJ Electric Fans

Just want to pass this info along-The Ford Contour or Mercury Mystique dual fan is a perfect fit on the CJ radiator and fits between the engine and radiator without clearance issues. Fits much better than the Taurus fan, which doesn't cover the entire radiator and usually has clearance issues.

That 400CFM is meaningless if 3400CFM is enough, even at 100F. On top of that, the Contour fan fit better to CJ radiators. These numbers are relevant when the fan shroud seal perfectly on the radiator, a small gap, mismatch, and the fan loose a substantial amount of CFM that pull through the rad.. So, with the Contour fans you get full capacity, with the Taurus on CJ radiator you get less than 3800CFM, might be even less than 3400CFM.
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I''m a big believer in variable speed controllers. A Delta Current Control FK-35 variable speed controller. The fans only run at the speed necessary to keep the coolant flowing back into the engine at the right temp, which most of the time is much less than full speed. On cooler days, the fan rarely runs when the Jeep is moving because airflow due to motion is enough to cool. Soft start and variable speed makes the fans very quiet. No current spikes.
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Just use the temp switch to activate the relay and the high speed fan will come on...

Now, for MAXIMUM Trail Redundancy, and absolute control of the fans,
(and using the cheapest & most common parts I could find!)
This will give you adjust ability of the low threshold setting,
The High threshold setting,
The fans will shut off when the engine shuts off,
The fans can run AFTER then engine shuts off,
The 'OVERRIDE' won't kill your battery if you forget and leave it on,
And you have a kill switch for deep water fording...

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For those guys that need a refresher on Relays
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Remember!
There is a 70 amp relay out there!
It's the starer relay for a Harley Davidson motorcycle if you need to order by application...

We use a lot of them on electric air compressors, They look like this,
(pay attention to the LOAD LUG SIZE! The small terminals the standard 1/4 Inch you are used to seeing!)
Ignore the air pressure switches, this picture is actually for the air system stuff, but the relays are the same...
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Now, most of you will try and find relays at the local Discount Auto Part Stores....

And you will be handed junk from China, Korea, South Africa, etc.
It's REALLY HARD to find a quality relay in the discount places!


Hella, Seimens, Bosch, etc. are th top quality companies, and you can find them by the loads for CHEAP in the junk yards!

This is really a diamond in the rough,
I got this at the local "U Pull" place for $1 and you couldn't put this together yourself for under $50
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Not only came with it's own mounting bracket, but has expansion room for another relay when I find it!
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WATER PROOF! 'Weather Pak' connectors,
Locking wiring harness so it can't vibrate off or be pulled off by water, hanging mud or anything else short of hooking up your tow strap to it!

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Top quality Hella relays! All of this for a one dollar bill!
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Don't forget to cut the wires far enough down the harness so you can use the GREAT connectors on these!
Also, these are the original fan relays from an '89 Cadillac.
The Resistors in the picture are 0.125 Ohm, 50 Watt each.

The Flex-a-Lite fan controller part number FLE31165 has a slow start feature on it of 60% and it gradually gets up to 100%. Has a override off, and override on feature as well. The cheapest I have found on line is here: [You must be registered and logged in to see this link.]

Another thought, has anybody thought of using 3 relays to run the twin fans in series/parallel to get two speeds out of them as seen in this diagram:
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see the cooling system diagrams. Notice that it shows the PCM controlling the speeds but the same could be accomplished with two temp sensors and over rides could be added with switches.

Another fan schematic, hand drawing. The relays are just common relays, #2 has the 87a post.
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Here is a different route, one controller for both speed, reading from the heater hose with direct contact with the water.
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This controller is an on/off controller and not a variable speed one, I don't like the e-fan working like a clutched fan, I would have stay with what I had.

The Controllercan be used with any kind of sensor (NTC, PTC, Pt100, TcJ, TcK, TcS) and can be calibrated. I chose the NTC thermistor option and used an external thermometer for calibrating it.

The set temp on and off is adjustable, I can set it to start at 210 and off at 202 or 209 for on and 200 off, or any other temp. range.
It's also replacing my additional temp gauge and it's that accurate that I can see when the thermostat is opening.

In case of a bad sensor the controller can be set to run the fan at high or low constantly.

There are two built in led indicating when either of the fan speed is on.

A buzzer can be added for overheating warning.

Now, with this controller the temp vary from 207F to 200, with the previous setup it was 220F-195.

The manufacturer is a well known in the refrigeration market. The controller can stand high levels of humidity and heat.

Thanks to RollBar, jeep hammer and the other numerous jeepers for the write up and the pics.