One thing to consider when doing this swap is the initial high amp draws upon starting the high-speed motor. One write-up reported that using a Fluke digital clamp ammeter; the starting draw the fan pulled was just over 130 amps, but only for a second. It then settled down to about 40 amps. Another reported that with the high speed completely blocked, it drew about 22 amps, and with the high speed unblocked it drew 18 amps, and the low speed drew only 9 amps. Not able to verify these numbers, I can tell you that with the engine at idle, there is a serious drain on the engine when I kick the fan on the high speed and that I can’t tell any difference when I turn it on low. My future plans are to install an 136-amp Mopar alternator or possibly an 140-amp alternator for a diesel engine. More on that swap as I complete it.

The other thing to factor in on this swap was how to mount the radiator overflow tank and the power steering reservoir. I would have completely destroyed the factory shroud by cutting it up to use just the reservoir mounts and I wanted to keep it whole incase I had to resort to the factory fan and shroud set-up. It also appeared that I couldn’t remount the shroud over the electric fan without a lot of surgery. And, I was looking forward to the extra space under the hood without the giant factory shroud. After a lot of research, I came across the installation instructions for the Flex-a-lite #475 I mentioned above. In those instructions, they mention a Reservoir Bracket Kit part #30927. I ordered the kit (a single bracket actually) from Summit and solved that problem.

Flip the fan upside down and locate mounting points (red dots)...

The first step is to remove the factory clutch fan and the fan shroud. I carefully removed the steering reservoir and the radiator overflow tank. I then removed the four nuts that hold the fan to the pulley and placed it inside the fan shroud. I then removed the four machine screws that hold the shroud to the radiator. Once the screws were out, I carefully pulled the fan and shroud out of the engine compartment paying special attention to not dent or damage the fins on the radiator. I then immediately replaced the nuts and tightened them down. I did this so I wouldn’t misplace them and to prevent the pulley from coming off which would have meant messing with the fan belt. Wow, what a giant space between the radiator and the engine. It looks as if I was missing two cylinders!

Remove the nuts that hold the clutch fan...

Once the fan and shroud are removed, it looks like I'm missing a couple of cylinders...

Room for a small refridgerator or cooler...

The Flex-a-lite bracket, with the mounting locations highlited in  red, the brackets in green, and the 4 bolts that mount everything together...

After pouring over many write-ups, I had several wiring diagrams to choose from. I knew that I wanted the ability to turn the fan completely off (for deep water or mud for example), to have the fan kick on automatically when the engine reached a certain temp and shut off when it cooled down to a certain temp, and to able to turn it on high when needed (like rock crawling in 100° heat). 

I wired my fan to this schematic…

I wanted to tap into a 12 volt switched source, although a few of the write-ups I read stated they wired their switches directly to the battery to allow the fan to run (and cool down) after they shut the engine off. Even though I’m running an Optima Red Top battery, I didn’t want to take the chance of draining the battery by going that route. On a really hot day, it could take quite a while to cool down an engine block and I don’t think using the fan after shutting the engine down would be that much faster. I ran three wires through the firewall into the cab by routing them through a grommet that is located slightly above and left of the clutch pedal.

Spot in firewall on the drivers side under the main wiring loom that the wires were ran through to the dash...

I ran them to the toggle switch that I mounted to one of the unused stock switch locations...

Switch wiring...

For the 12 volt switched source, I tapped into the main fuse/relay box under the hood. By taking off the cover, I could see a couple of unused relays (ABS & an AUX. Fan) that I used a circuit tester to find the switched input on.

In the picture below #1 is the center wire from the toggle switch, the arrows by #3 show the hot/switched leads, and #2 is the wire I used from #3...

I pulled one out of the relay location and spliced it to the wire that supplies the dash switch. If I were to do it over again, I’d run all of the wires into the bottom of the fuse/relay box and tie into the two unused relay locations utilizing factory relays. I think that it would look a lot cleaner as far as the wiring would go. I spliced the red power wires coming off the relays together and spliced in a 30-amp fuse before connecting to the positive power supply on the battery.

By lifting up the fuse/relay box, I could use the boxes mounting screw to hold the relays...

On the end closest to the battery there is a positive supply that is held down by a ½” nut that I use for all of my power instead of connecting directly to the battery. There is a plastic cover that pops off to access this. I crimped on a round end connector and tightened it under the ½” nut. I grounded both relays to a ground by using a self-tapping screw into the fender well next to the fuse/relay box and I grounded the fan itself to a ground location right above the passenger’s side headlight. Basically, all of this sounds harder than it really is. If you take some time to understand how the relays work and stick to the wiring schematic, it is quite simple.

A quick course in Relay 101; all basic automotive relays have either 4 or 5 prongs with each prong labeled a different number. In my research, I saw many wiring diagrams that were wired backwards, but worked due to the basic principles in electricity. When looking at the relay, the 30 tab feeds the power from the battery to whatever you are running, with the 87 or 87a tabs connecting to (in this case) the fan. The 85 tab runs power from the switched source to open (87) or close (87a) the circuit, turning on (or off) the fan. The 86 tab is the ground. So basically, you flip the switch on your dash that sends enough power to the relay to connect the circuit, turning the fan on. One way to use only one relay for both speeds would be to wire the high speed to 87 and the low to 87a and use a 2-position switch to toggle between the two. However, by going this route, you would never be able to shut the fan off.

On several of the write-ups I noticed that they suggested using a 1N4007 diode between each of the fans power wire and it’s ground wire. The suggested reason for using the diodes is explained by the fact that the electric fan can still generate a charge after the vehicle is shut off, as it is basically an electric generator. Using the inexpensive diodes allows the fan to discharge the excess electricity safely, resulting in greater longevity for the fan’s motor. A lot of the fan wiring kits have an extra wire that runs between the relay and the thermostat that can be hooked up to the A/C clutch so that the fan comes on when you run the air. For those without A/C, you can wire it up to a toggle switch for the basic on/off function. This is ok for a single speed fan set-up, but was an extra (unneeded) step for my set-up so I eliminated it.

After checking and rechecking all of the connections, I started the Jeep and took it for a test drive. The fan kicked on when it was supposed to and kept the Jeep at the desired engine temp of 210°. I flipped the switch and could hear the whine of the high-speed fan. There was no noticeable increase in horsepower, but I imagine that it would be hard to tell the difference by adding only a couple horsepower anyway. I’ll report back after using it for a while!

Finished install. Other than trying to hide the ugly wire and connector colors with a loom and replacing my quick-fix wire ties with some black zip-ties, it looks like a factory install...

Here are a couple more wiring schematics I ran across in my research that could help you if you decide to wire your fan different. HTH!

Single relay, single speed fan...

Another one that is wired to turn on low with the thermostat switch or be turned on low manually through a toggle switch. The high comes on only when the A/C is running...