Writeup: Replacing the Mechanical Fan w. another OEM Aux Fan

[hubs97xj]

Feel stupid for not Googling that earlier, but the scotch was making me think funny. Okay, definitely not going to be as cheap as I'd hoped, but then again, it never is, is it? Also seem to be backordered everywhere I've looked so far.

Could just do the relay and harness, but I like the idea of being able to set it for whatever temps I want, and also spinning it slower/quieter. Guess I'll push this one back a while unless I find a deal like Comanche scored.

Thanks for the info

 

[srimes]

I used a Spal variable speed controller to independently control the new fan only, which is now my primary cooling fan. The LO speed is set to come on a 190*, and the HI speed at 215*. So far these settings are working fine, with the new fan staying 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. But I did want redundancy just in case, so I wired in a dash switch so I could turn this fan on manually if the new primary fan went belly-up.

So far all is well, the new fan runs 90% of the time in LO, only coming on HI speed when stuck in traffic for some time. The existing aux fan has never come on (except when I run the A/C of course. I also have noticed a mile or two increase in MPG on the stroker, which helps. The engine seems to spool up faster too w/o because it's not pulling the old mechanical fan, but this may be my imagination. And changing either fan is now a 15 minute job. Hope this helps someone who is considering doing this mod.

Great writeup, thanks man. I've been thinking of doing this myself.

I think you've set the new fan temps too low. The fan should not turn on before the thermostat is fully open and it shouln't run 90% of the time with normal driving. It's a waste of energy and will wear out the fan.

I ran with only the aux fan for a while and on most trips it never turned on except for a/c useage. It usually only turned on if I was waiting in a drive-through line.

When I do my setup I'll probably just have the new fan triggered with the aux fan, but if I had a seperate control I wouldn't set the low turn-on temp any lower than 210-215. You want it off as much as possible.

 

[comanche91]

Great writeup, thanks man. I've been thinking of doing this myself.

I think you've set the new fan temps too low. The fan should not turn on before the thermostat is fully open and it shouln't run 90% of the time with normal driving. It's a waste of energy and will wear out the fan.

I ran with only the aux fan for a while and on most trips it never turned on except for a/c useage. It usually only turned on if I was waiting in a drive-through line.

When I do my setup I'll probably just have the new fan triggered with the aux fan, but if I had a seperate control I wouldn't set the low turn-on temp any lower than 210-215. You want it off as much as possible.

Trouble is the Spal PWM controller needs a minimum of 20* DC delta between the LO and HI settings, otherwise it doesn't work. Setting the LO at 210 would mean the HI comes on at 230* and I don't want it to get that hot. But I'm still experimenting. I plan to replace the square blade w. a newer curved blade and will try the higher temp settings then. But your logic is spot on.

 

[ehall]

I would think the best thermal target would be the same as whatever causes the thermomechanical clutch fan come on

 

[Slo-Sho]

I use a 3 terminal sensor from an 80's Saab. Has integrated Hi/Lo thermistors, very similar to what is used on the Renix setup except it has dual temp triggers instead of the one.

 

[XXX]

I use a 3 terminal sensor from an 80's Saab. Has integrated Hi/Lo thermistors, very similar to what is used on the Renix setup except it has dual temp triggers instead of the one.

Would this application fit in the thermostat housing?.....or is it metric thread?

 

[comanche91]

I use a 3 terminal sensor from an 80's Saab. Has integrated Hi/Lo thermistors, very similar to what is used on the Renix setup except it has dual temp triggers instead of the one.

Slo - Is that Saab sensor like the one below, Standard p/n SITX18?

 

[Achmed]

I use an aadjustable thermostatic fan controller from O'reilly Auto Parts to control my second electric fan. You can set it to come on and off where you want. Perfect results here. Total invested:

(1) 14"/2200CFM curved blade fan - $29.00 shipped.
(1) 40 amp relay - $3.00
(1) Thermostatic Fan Controller - $18.00

Total: $50.00 and my temps stay right where they need to and I dont have a dragging mechanical fan clutch to deal with.

 

[Boostwerks.com]

I use an aadjustable thermostatic fan controller from O'reilly Auto Parts to control my second electric fan. You can set it to come on and off where you want. Perfect results here. Total invested:

(1) 14"/2200CFM curved blade fan - $29.00 shipped.
(1) 40 amp relay - $3.00
(1) Thermostatic Fan Controller - $18.00

Total: $50.00 and my temps stay right where they need to and I dont have a dragging mechanical fan clutch to deal with.

Bingo. I would rather have a simple fan switch compared to a controller. Theres absolutely no need for the fan to have two different temp settings or fan speeds. Case in point: every car mfg that has dual electric fans uses a switch.

 

[comanche91]

Bingo. I would rather have a simple fan switch compared to a controller. Theres absolutely no need for the fan to have two different temp settings or fan speeds. Case in point: every car mfg that has dual electric fans uses a switch.

Case in point - you're wrong. Nearly every vehicle manufactured since 2004 uses some kind of variable speed fan control for at least one of the fans. Even some early 90s Benz's I had used multispeed fan control. Some use a PWM based controller like the Spal, or a variable linear output voltage based on engine temperature from the computer. And the reason for the variable speed fan(s) is to prolong the electric fan lifespan, save unnecessary load on the electrical system, and reduce noise.

 

[Achmed]

Ehh. I think you are shooting in the dark and putting WAY too much time, effort and money into such a plan. I posted a simple, logical, affordable and very sensible solution above. Your XJ is not that intelligent to need such a hodge podge setup.

 

[comanche91]

Ehh. I think you are shooting in the dark and putting WAY too much time, effort and money into such a plan. I posted a simple, logical, affordable and very sensible solution above. Your XJ is not that intelligent to need such a hodge podge setup.

My total outlay so far has been $55, for the Spal controller (looks like they cost more $$ now though). I used an existing XJ aux fan I've had around for years. No external sensor needed, no relay needed, or additional wiring; these are all built in to the Spal controller. This is much simpler system than yours; your's has too many points of failure. And I do have a manual fan control switch wired in if needed. Oh, and it's an MJ, not an XJ. :clap:

 

[xSUx SGT BAKER]

Ehh. I think you are shooting in the dark and putting WAY too much time, effort and money into such a plan. I posted a simple, logical, affordable and very sensible solution above. Your XJ is not that intelligent to need such a hodge podge setup.

This is why i love forums. comanche91 did a wonderful write up on a fan setup that he is using and naturally some one fells the need to bash it. Yes you did post "a simple, logical, affordable and very sensible solution" but lets remember that the original thread was a write up on how comanche91 installed a dual electric fan setup up on HIS jeep. But now this thread has been polluted with senseless bashing:lecture:


on another note, great job on the write up. :worship:

 

[Achmed]

I didnt bash it, but I added my opinion. It's a forum. Forums are opinion based.

The End.

 

[comanche91]

This is why i love forums. comanche91 did a wonderful write up on a fan setup that he is using and naturally some one fells the need to bash it. Yes you did post "a simple, logical, affordable and very sensible solution" but lets remember that the original thread was a write up on how comanche91 installed a dual electric fan setup up on HIS jeep. But now this thread has been polluted with senseless bashing:lecture:

on another note, great job on the write up. :worship:

Thank you SGT. Open forums like are intended for all to express their opinions, either positively or negatively. I don't mind either, because you almost always learn something constructive from every post. There are many opinions of the best ways to implement solutions that improve the driveability of our rigs. This was my considered best bet to eliminate the mechanical fan, maintain at a minimum the same cooling effectiveness, and perhaps benefit the MPG and usable HP numbers. Feel free to use it or not - no matter to me, and no offense taken. :cheers:

 

[Achmed]

Anyway comanche91..........................good write up and I am glad your setup works well. No need to take my post like Baker did and get fussy.

 

[comanche91]

Anyway comanche91..........................good write up and I am glad your setup works well. No need to take my post like Baker did and get fussy.

Thanks mate. But SGT Baker was also expressing his opinion, which I completely agree with. :yelclap:

 

[hubs97xj]

Got some P/Ns?

 

[xSUx SGT BAKER]

Im sorry if i came off like a turd in my last post but i consider "Ehh. I think you are shooting in the dark and putting WAY too much time, effort and money into such a plan." a bash. maybe its just me :looney:. either way, both ideas are great ones, and i always respect others opinions.:cheers:

 

[themud]

2 Questions for ya...

1 Could you not simply the wiring and just wire up both fans to come on together IE youd use even less fan power as they are both working together and the spal can control them both at the same time???

2 How did you plan to draw air through the 5 inches of radiator not covered by the fan shroud of the primary fan, In AZ we need every amount of cooling we can find to help keep the jeeps cool in 118* weather especially in stop and go traffic??

Otherwise looking to try this on my rig but would want to use both fans at lower speed to help keep things cool...
themud