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View Full Version : Dual Electric Fans Using Two Stock Aux Fans



Comanche91
01-20-2013, 07:33 PM
I had been wanting to dump the antiquated mechanical fan for a while on my MJ, and have been looking at various "how-to's" on Dino's and Gojeep's websites, among others. One criterion I had was that I wanted to keep it restorable if I ever wanted to go back to the mechanical fan, so I did not want to cut the existing mechanical pulley shaft as Gojeep did, which was necessary for clearance using the large 16" fans. After looking at various installs, I decided to go a similar route as NAXJA's Slo-sho did and replace the mechanical fan with another XJ/MJ OEM electric aux fan, but with a few mods. These fans pull a lot of air for their size (about 1350 CFM) and I had a couple of spares readily available.

Step one of course is to remove the old radiator and mechanical fan blade, shroud, and clutch. Then I replaced the fan pulley studs with 5/16" x 24 x 3/4" button head bolts which provide more fan clearance than hex-head bolts .

Pulley clearance using the stock hex-head bolts:

http://i182.photobucket.com/albums/x297/comanche91/fanmod5-1.jpg

Pulley clearance using the button head bolts:

http://i182.photobucket.com/albums/x297/comanche91/clearance.jpg

I wanted to use a quality all-aluminum rad for better side tank heat transfer. This is the one I used from FFD, minus the fans of course. It's a solid dual core all metal that I've read good things about. $200 shipped, here's the link http://www.ffdynamics.com/jeepradB1.html:

http://www.ffdynamics.com/images/jeep1.jpg

Since welding new aluminum mounting tabs was impossible due to the core being too close to the bottom support bracket, I had to modify it. I fabbed a new support brace out of 1/2" angle aluminum across the bottom and used a Dremel to cut two new slots out for the second fan mounting tabs as below:

http://i182.photobucket.com/albums/x297/comanche91/1-3.jpg

http://i182.photobucket.com/albums/x297/comanche91/4-2.jpg

http://i182.photobucket.com/albums/x297/comanche91/3-2.jpg

Mockup:

http://i182.photobucket.com/albums/x297/comanche91/5-5.jpg

This setup fits great, and the new aux fan shroud is very close (but not touching) the radiator which increases it's efficiency. I did have to trim the new fan shroud about 1/4" to make sure it was not touching the radiator.

Since this pic was taken I've swapped out the eight blade fan on the left with a 1999+ 10-curved blade fan like the other as they are quieter and have a higher CFM rating:

Here's a rear view of the two electric fans installed:

http://i182.photobucket.com/albums/x297/comanche91/fanmod4.jpg

And a front view:

http://i182.photobucket.com/albums/x297/comanche91/fanmod3.jpg

I used a Spal PWM-V1 variable speed controller to independently control the new fan, which is now my primary cooling fan. For temperature sensing input to the Spal controller I used the existing dash gauge temp sensor located at the left rear of the cylinder head. I first tried the ECU temp sensor on the thermostat cover, but the gauge sensor on the head provided a larger voltage delta between the Spal LO and HI fan speed settings and gave more precise fan speed-switching control than the one on the thermostat cover. I programmed the controller for the fan LO speed to come on at 190* and the HI speed at 215*. So far these settings are working fine, with the new fan running on LO most of the time. The existing aux fan still operates as always, ON with the A/C or when the temp reaches 220* or so. I did want redundancy just in case the new electric fan or controller failed, so I wired in a dash switch that supplies a ground signal to the aux fan coil relay in the PDU and allows manual control of the existing aux fan. The schematic is shown below:

http://i182.photobucket.com/albums/x297/comanche91/fan3-1.jpg

http://i182.photobucket.com/albums/x297/comanche91/AuxfanWiring.jpg

I've had this setup up and running for a few years now, and it works well. The new fan when it runs is about 90% of the time in LO, only coming on HI speed when stuck in stop and go traffic. The existing aux fan has never come on it's own (except when I run the A/C of course). I also have noticed a slight MPG improvement since the engine doesn't need to pull the old mechanical fan load anymore. The engine seems to spool up faster too, but this is probably my imagination. I hope this brief writeup helps someone who is considering doing a dual electric fan mod.

Brasscatz
01-20-2013, 09:22 PM
Looks great man! Maybe you included it and I didn't see it, but do you have a link to that radiator?

shim89xj
01-20-2013, 09:32 PM
Dual electric fans have to be my 1989.
http://shim89xj.blog63.fc2.com/blog-entry-120.html

In Japan, there is a good controller.
http://shim89xj.blog63.fc2.com/blog-entry-134.html

Comanche91
01-20-2013, 09:45 PM
Looks great man! Maybe you included it and I didn't see it, but do you have a link to that radiator?

Link: http://www.ffdynamics.com/jeepradB1.html

I called FFD and asked the price for the rad only. I don't know what the price is now though as I purchased it a few years ago. I'll edit my post and include the link in the post, thanks for the reminder.

Pookapotamus
01-21-2013, 09:10 AM
what did you think of the quality of the rad? very interested as i am looking for a fan and rad kit for my build.

Comanche91
01-21-2013, 10:49 AM
what did you think of the quality of the rad? very interested as i am looking for a fan and rad kit for my build.

It's a well constructed radiator. I have been through quite a few single core and three core rads and this one performed the best for me.

MattybPDX
06-06-2017, 11:11 AM
4 years later this is my reference for my next project. Gotta love when Google brings me back to xjtalk.

Sent from my SM-G935V using Tapatalk

bluedragon436
06-06-2017, 08:14 PM
4 years later this is my reference for my next project. Gotta love when Google brings me back to xjtalk.

Sent from my SM-G935V using Tapatalk

Darn near everything I look up online when I'm stuck on something, whether it be my XJ or someone else's XJ... One of the first results usually brings me back to :xjtalk1: so of course I have to select that one for help... :keegirl: