Topic: FoMoCo Electric Fan Conversion

[Jeffy]

Everyone talked about the Ford Taurus fan and while it is a good fan, it's not the only one out there.  FoMoCo has used the same 2-speed motor on several different vehicles over the years.  The Taurus is a 17" fan is the most popular since it's the first.  Volvo's also use the same 2-speed motor.  The Lincoln MKVIII is what I ended up with.  Unlike the Taurus fan the Lincoln uses an 18" fan.  The fan measures 18"x22"x3" at the shroud.  It is huge.  The fan will cover 100% of the radiator surface which makes it fairly simple to mount with minimal fabrication.



I ended up making some L brackets out of galvanized plate that was punched full of holes.  With some sheet metal shears, the plate was cut into strips about 1" wide.  Each strip was cut to 2.25" and was bent at 1.25".  The shorter end was then drilled with over-sized to allow for lining up the fan to the radiator.  I drilled two holes for sheet metal screws on the other side.  The bracket would attach to the inside of the shroud with the screws sandwiching the shroud.  While you're at it, cut the plastic arms off the shroud.  They will only get in the way and since they are recessed, they are too far back to be usable.  If you have a TJ, you'll need to either buy or fabricate a bracket for the radiator overflow reservoir.  For a YJ, there is no need and the Power Steering Reservoir can be remounted in the original position.



So now you have the easy part done.  Most people will cringe when having to do anything electrical.  It's fairly easy though.  The fan will have three wires in the harness.  The black one will always be ground.  The blue is the slow-speed led.  The high-speed led will either be brown with an orange stripe and be noticeable thicker gauge.  You don't want to confuse the low and high speed leads.  You will need a relay.  If you choose to use the slow lead, then you can use a 40A Bosch type relay.  If you choose to use the high speed led, you will need a relay in the 75/80A range.  If you choose to use a adjustable thermostat then you'll need to wire that in as well.  I ended up wiring the fan so it turns on and stays on with the key.  I will probably install a adj. thermostat which will turn off the fan when it reaches a certain temperature.  In the schematic diagram I have included, you would wire the thermostat into Keyed 12v 86 circuit.



I have found that the slow speed is still very fast and pulls a LOT more air then the stock clutch fan.  I really don't think there is a need to use the high speed circuit.  Small animals and children could be sucked into the radiator.  This bring up another issue.  The fan pulls some heavy amps.  If you run a stereo, aux lights, gps, or have a winch, you will really want to upgrade your alternator to something over 100amps.  This will be required to run the fan.  Otherwise, your battery could end up being drained.

[Jesse-James]

Any noticable difference on the butt dyno or does it feel about the same?

[Jeffy]

Any noticable difference on the butt dyno or does it feel about the same?

There is a definite change.  I'm having to readjust using the clutch and throttle.  The engine revs more freely so starting from a stock will seem a bit quicker.  I haven't driven the Jeep far enough no on the highways to notice any other differences.  Although, I'm sure there is more available torque since the engine has less accessories to turn.

For us YJ'ers though, I think a alternator upgrade is a really good idea.  Before my Volt meter was at a steady 14v on the gauge.  Now it's past 14v, so it is working harder.  I've only driven around with the fan , iPod and stereo and headlights on.  I'd hate to add another 110w load on there.  It would really suck if I had to do some night winching as well.  I've watched the Voltage gauge with nothing but the ignition ON and the gauge starts to drop into red with the fan running.  I'd hate to have teh ran run independently from the Key'ed ignition like on some new cars.  You'd walk back and your battery would be dead. 

Hopefully when the new alternator arrives all the power issues will be gone.

[Jeffy]

I finally got around to adding a switch and a adjustable thermostat to control the fan.  This is extremely helpful in the winter months as the engine will take forever to heat up with the fan going.  This also saves power as the alternator won't have to work as much, especially when on the highways where it should turn off.  Nothing to fancy here.  I went with a inexpensive Flex-A-Lite adjustable thermostat unit.  It has a rheostat that can be controlled to turn on at 160-240*.  Some experimenting will be required to set it up.  The probe will need to be passed through the radiator.  The best location is as close as possible to the inlet at the top of the radiator.  I was able to slip the probe through an existing gap at the top of the fins directly under the inlet.  I had to remove the fan to gain access to the radiator though.  How much room available for the probe will depend on the fan.  With the MK8 fan, there is plenty of room for the probe as well as the wire.

Wiring up the thermostat is very easy since the relay was already done.  All that needed to be changed was pin 86 on the relay needed to be moved to the thermostat and a jumper back to the relay.  That's it.  Oh, you will notice the idle stumble as you're sitting at a light and the fan kicks in.  This is normal as the alternator does kick in suddenly.

[Jeffy]

Here's an update since it's been a while since I've updated the post.  Instead if using a ATC fuse and holder I moved to a post type circuit breaker.  The reason being, the blade fuse holder doesn't have enough contact with the fuse.  After a while, the additional resistance will cause heat and melt your fuse holder and ultimately the fuse.  Some ATC fuse holders are good for up to 40A but most are 20A cheap ones.  You could move up to a MAXI fuse holder but they are significantly more expensive and harder to find on the road.  So I went with a 40A circuit breaker and changed the wiring to 8 Gauge on the +12v side.  Instead of terminal connectors the CB uses nice ring connector so there is no worry of a weak connection.



The relay will still use a terminal connector.  If you want to move up to a screw-on terminal, you'll need to more to a 75A Bosch/Tyco Automotive relay.  So far I've been OK with the 40A Bosch/Tyco relay.  I did use pliers to tighten the terminals so they aren't loose on the relay.  If you don't do this the relay will probably melt over time.  This could loosens the terminal and loses connection internally.

I have also installed an adjustable thermostat controller from Flex-A-lite.  It's the cheap one.  I found that if you crank the dial to it's lowest temp, the fan should be off when moving but turn on soon after you stop.  The instructions say it can control a fan without any additional hardware but this isn't a good idea with a high-amp fan like the Mark VIII or the Taurus fan.  When installing it, you have three choices but the best is probably on the switch side.  If you use the +12v or -12v, the controller will turn into a high-amp switch.  Most of these controllers are able to deal with 30A but not much more.  Since the keyed +12v is a low-amp trigger, it's better to wire the controller into that circuit.