dual electric fans wiring

So I picked up a second stock e fan to hook up and run two electric fans. I got it installed and everything and I thought it was wired correctly. The fans both run together but they come on as soon as the jeep starts and run continuously. I want them both to work as the stock one does. Coming on at 218 and when the ac is on. I found plenty of threads on how to install the fans but none told me the correct way to wire it. Can anyone show me a wire diagram on how to hook the new e fan to the stock e fan and have it run like the original. Thanks

you know that won't be enough airflow, right?

I found tons of posts on people running that set up with no problems at all

metric or standard tons?

if it was metric, it'd be a tonne.

70hemicuda said:

I found tons of posts on people running that set up with no problems at all

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after 10 years on naxja, you learn some patterns.

one of the patterns you see is those same people who say it has no problems show up a few months later with cooling problems, and or a blown head gasket.

It really is not enough air flow. It is tonnes short..

70hemi, you could splice the negative wire from your number 1 fan that is signaled by the CTS to positive at fan number 2 and from there run that fans negative wire to a ground with in the engine bay.

something does not feel right about trying to run a pair of 12v fans in series on a 12v electrical system

People float the number that the AC fan is good for 2500.
I ran a fan advertised at 2150 full-time and I ran it computer controlled.
In neither case was it *close* to as effective as the mechanical fan I replaced.
If you are going electric, be very honest with yourself about how you use the Jeep.
Even in mild Berkeley, CA weather - a full time 2150 CFM fan wasn't up to snuff going around town. Towing, it was near-disastrous. Seriously. Oil pressure & coolant temp both moving in the wrong direction, sounded like pinging, a real mess. Shortly after, I put the mechanical back on.
I've recently gone even more the other way and put a ZJ fan clutch in it. No regrets, either.

I dont know where people get that number. Its closer to 4500 cfm.

The next time I have the winch off of 4643 I'll borrow an anemometer from our AC guy at work and get hard numbers.


2500 may be with a light duty clutch and a cold engine, before things start to engage?

yossarian19 said:

People float the number that the AC fan is good for 2500.
I ran a fan advertised at 2150 full-time and I ran it computer controlled.
In neither case was it *close* to as effective as the mechanical fan I replaced.
If you are going electric, be very honest with yourself about how you use the Jeep.
Even in mild Berkeley, CA weather - a full time 2150 CFM fan wasn't up to snuff going around town. Towing, it was near-disastrous. Seriously. Oil pressure & coolant temp both moving in the wrong direction, sounded like pinging, a real mess. Shortly after, I put the mechanical back on.
I've recently gone even more the other way and put a ZJ fan clutch in it. No regrets, either.

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No stock xj 4.0 needs a zj fan clutch, or any other cooling system mods for that matter. I live in the desert, daily drive my jeep, wheel when it's way too hot, and my jeep is heavier than most (1 ton axles, 37's, etc) and i rarely ever get to 215. Completely stock cooling system.

LOL nice pic.
I figured the XJ fan clutch was 16 years old with ~150K on it. Just "due". Same dollars, same amount of work, why not move more air? The goal was / is to minimize reliance on the aux fan to keep things in check. No particularly good reason, as, I agree - if everything is in good shape, the stock cooling works just fine.
Cal - I'm talking about the AC / electric fan that came in the XJ. Are you? I think you are talking about the mech fan... Which, yes, moves a lot of air. Dr. Dyno was claiming 1700 CFM at idle, though I don't know if that was cold or hot (or if the number is good in the first place). Anyhow

What problem are you trying to fix by adding a efan instead of the mech?
As stated the stock stuff works. Just got done changing back to a mech fan from a second efan because I was trying to fix a problem that wasn't there.
Sure it will free up about 5 hp, but your heep will get hot. This is with an all new cooling system too

My fan clutch was going out so I swapped in a late model efan with the curved blades. This is on a 99 so it already had that same fan right next to it. I wired it via relay to cut off and on when the stock one does. Works fine here in Texas.

DeftwillP said:

My fan clutch was going out so I swapped in a late model efan with the curved blades. This is on a 99 so it already had that same fan right next to it. I wired it via relay to cut off and on when the stock one does. Works fine here in Texas.

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How did you wire it to the stock one?

cal said:

I dont know where people get that number. Its closer to 4500 cfm.

The next time I have the winch off of 4643 I'll borrow an anemometer from our AC guy at work and get hard numbers.


2500 may be with a light duty clutch and a cold engine, before things start to engage?

Click to expand...

I too will like to see some real numbers.

The debate "Go electric", "Go Mechanical" never ceases. When I did the conversion to electric fans I used the Go-Jeep's site for reference. It stated that the 4.0L need a minimum of 2000 CFM for normal driving with a good cooling system and 2500+ if towing or going up hill. It think it was based on some BTU calculations of the 4.0L, the size of the engine room etc. I went beyond that suggestion and got me a dual fan setup rated at 4000 CFM. It was expensive to buy and not a drop in replacement. They have served me well over the years with no regrets whatsoever.

However, knowing what I know now, I would have renewed and kept the OEM mechanical fan. When I did the retrofit, the problems I experienced were high temperature in stop and go traffic or when going through a drive through.The E fan would come on in both instances and bring the temperature back down to where it should. I flushed the entire cooling system, replaced the radiator, thermostat and water pump along with the dual E fans all at the same time. Which one solved the problem or was it a combination of everything I will never know.

Finally, if your XJ are having cooling issues, isolate and replace the defective part or parts with good quality parts,... no after market bargain priced parts. An E fan is not the magic portion to cure all ever heating problems. Saving 5 HP's or 10 HP's by ditching the mechanical fan?....my butt dyno is not that finely calibrated.

Since the efforts to try and sway you into not getting rid of the mech fan seem to have failed. I'll go ahead and tell you how to wire it.
Tee into the positive wire going to the stock efan, run that new wire to the switched 12v terminal on a regular 12v 30-40amp relay.
Run a power wire from your battery to the constant power terminal on the 12v relay. Ground the relay on the grind terminal.
Run a wire from the switched 12v feed terminal to the new efan positive wire.
Ground the new efan ground wire.
Look up in a general search engine "12v 4 terminal relay wiring" to see what numbers on the relay correspond to the terms I used above.
Use wire that is sized at least the same size at what is on the existing efan. I am pretty sure it's 12g.

O and put a inline fuse on the wire from the battery. Use the same size as what the stock efan uses. Check the fuse panel to see what it is.

Thank you. And I'm not having over heating problems. I just like the idea of having two efans because I do some deep water crossings now and then and the ability to turn the fans of and savery my radiator really helps.

why not just splice the relay signal from the ECU and control a second relay? Or replace the existing relay with a higher rated relay and increase the wire size from the relay to the fans? Lots of ways to do it, I don't think just simply splicing into the positive wire at the fan is the right choice though, you need to account for double the current in the wires and through the relay

wait, if you want to have direct control over the fans why didn't you say that? If you want full control, just run a switch inside wired to the relay ground. If you want partial control, cut the ground to the stock relay and run that through a switch so you can have the computer control the fan all the time except when you switch it off. Same wires could be used to control the second relay ground for the second fan before running to the switch.