HOW TO: Make Room for and Install an Electric Fan

[lost honda pro]

Alright, I've done a bunch of research on this, and I've yet to come across a writeup for a USDM 97+ XJ, so I'm gonna do one. Let me add that I didn't have any problems with my cooling system, it worked flawlessly, I just wanted to be able to control more cooling at/near idle, without running the A/C. Here's how this thread's going to look:

Part 1: Mechanical Fan removal & Belt re-routing

Part 2: Picking a Fan

Part 3: Installing Electric Fan

Part 4: Wiring

Part 5: Cost Breakdown



***** Part 1: Mechanical Fan Removal & Belt re-routing *****

This is VERY straightforward. There are two small bolts at the top of the fan shroud, and four nuts on the fan clutch. Remove all six, and the fan/shroud with come out the top easily.

Once it's out, you can see that there's only like 2.75" to mount a fan/shroud. It can be done, but the options are slim, especially when trying to get 2000+ CFM. So, the best bet is to remove that fan pulley entirely, since it's now useless. I looked at several other fan installs, and noticed that the pre-97 XJs had an idler pulley next to the thermostat housing. I realized I could use this pulley (mounted on the A/C compressor bracket) to re-route the serpentine belt, eliminating the now useless fan pulley. This is how the belt will look:

Went to the junkyard, and grabbed up this A/C bracket off a '91 for $14:

Using a 4.5" angle grinder, I chopped off the shaft and support for the fan pulley (all this so I had the option to go back to stock, I wasn't sure it was gonna work out right...)

This is how it looks with the modified A/C bracket, and the belt routed (temporarily):

I also bought a spare front alternator bracket, as the new belt would have gone through it, as seen here:

The red lines are the belt outlines, and 1) is the timing cover stud that had to be ground smooth, 2) is the alternator bracket that was modified. It was modified like this:

So that it woulf fit between the top bolt of the alternator bracket and the bolt/nut combo that goes through the bottom of the A/C bracket. Using some lock washers as spacers, it came together perfectly. The A/C bracket bolt hole had to be opened up a bit, but it fits like this:

 

[lost honda pro]

This is the final belt clearance. 1) is the belt, 2) the upper half of the alternator bracket, 3) the lower half. Plenty of clearance:

And how much space you now have, note that the upper alternator bracket doesn't stick out past the belt:

***** Part 2: Picking a Fan ******

There are almost endless electric fans to choose from, and there are a few simple parameters you should follow when selecting one:

1) space contraints: you have about 17.5" wide by 11.5" high of radiator core to cool, so a 10" fan is too small, and an 18" fan is too big. 12", 14", and some say a 16" are the best choices

2) CFM: you need to pull (supposedly) around 2000 CFM to keep this motor happy. After I removed my mechanical fan, I used the little 11" auxiliary fan to keep me cool at lights and in traffic, and although the A/C was never on, it did manage to keep me at 210*F. So if you are running the A/C, in traffic, towing, or crawling a lot, you will need more.

3) Amp draw: most fans will draw 20-40 amps on startup, and settle down to 8-12 amps steady state. This usually isn't a deciding factor, unless you're doing a Taurus fan, which is rumored to draw anywhere from 60-90 amps on startup.

4) Here are the most usefull writeups I've found:

Dino Saava - 1800 CFM - 14" - http://www.angelfire.com/my/fan/electric.html

Marcus (Go Jeep XJ) - 4500 CFM - Taurus Fan - http://www.go.jeep-xj.info/HowtoTaurusFanInstall1.htm

Maud'Dib () - 4500 CFM - Taurus Fan - http://www.go.jeep-xj.info/HowtoTaurusFanInstall2.htm

Marcus (Go Jeep XJ) - 2500 CFM - 16" ICE Fan - http://www.go.jeep-xj.info/HowtoElectricFan.htm

Chuck (JC95) - 3300 CFM - 16" Zirgo Fan - http://www.go.jeep-xj.info/HowtoZirgoFan.htm

John Wood - 2950 CFM - 16" Perma Cool Fan (bottom of page) - http://www.go.jeep-xj.info/HowtoElectricFan.htm

5) I chose to run a Perma Cool 19114, 14" 2950 CFM fan. It's 3.75" thick (only in a small spot), has an open metal frame, pulls a ton of air, and only draws 30 amp startup/9.5 continuous. It fits great, and should handle any towing/traffic/crawling I can throw at it. The only downside is the $125 price tag:

http://www.jegs.com/i/Perma-Cool/771/19114/10002/-1

 

[lost honda pro]

***** Part 3: Installing Electric Fan ******

While almost every aftermarket fan comes with the "zip tie & foam pad" mounting system (zip tie the fan to your radiator core), most everyone (including some manufacturers) will recommend you NOT use this on an off-road vehicle, as the flexing of the chassis/radiator core could result in your fan carving a nice hole in the radiator core. Some of the writeups referenced above suggest using the OE fan shroud, which looks like a great option, but I wanted my fan as tight against the radiator as possible, so I made a shroud out of 22 gauge sheet metal. The first step is making a paper template to check clearance:

Once you've got a design that fits well, trace it and cut it out:

I took it to a local fab shop and one of their guys bent up the edges for me:

Then I cut the center out, and test fit it:

After a few minor modifications, I bolted the fan on, and test fitted the whole assembly:

 

[lost honda pro]

There's a little over an inch between the bulge in the fan motor and any engine components. I call that a perfect fit:

After a good alcohol bath, I hit it with two coats of Rustoleum, added the fan, threw it in, and re-routed the overflow hose:

** UPDATE **

After wiring this setup, I tested it and was not impressed with it's performance. I had to space the fan out from the radiator core in order to keep it from contacting the hood release bar, and I think this put the fan too far from the core (~1.5"). I ended up removing the upper radiator support, bending the bars on the fan, and mounting it directly to the upper radiator support. I also made some little tabs to mount the bottom two fan brackets. With this setup, the price drops (no $18 sheetmetal) and the fan works better. It looks like this:

 

[lost honda pro]

***** Part 4: Wiring *****


I'm powering it using a Radio Shack 40A mechanical relay, 30A fuse (per Perma Cool's instructions), and 10 gauge wire. The fan will be wired in parallel with the OE Auxiliary fan, so that it will be activated by the ECM when either 1) the A/C is turned on, or 2) the engine temp rises above 218*F. I will also have a switch to activate both fans if I choose to (for crawling/idling/towing). I finally found a flawless method of adding a switch and not getting a CEL, for a reasonable price and a bit of work. It will work like this:

NOTE: the diode I used is actually a type 4004, not 4005. And the resistance that I never filled in is a 100 ohm.

I can't take any credit for it, however, as the idea for the DPDT switch came from a member on the All About Circuits forum. Here's the thread:

http://forum.allaboutcircuits.com/showthread.php?t=19150

And this is the suggestion I got from the guy on that page:

I got this switch from Radio Shack... not exactly what I wanted, but it fits there, and doesn't have a 'center-off' feature. It works well:

I simply put a hole in the empty slot next to my rear wiper switch:

And it ends up looking like this:

***** Part 5: Cost Breakdown *****


Perma Cool #19114, shipped $137

'91-'96 A/C bracket $15

'91-'01 Alternator bracket $8

New idler pulley $17

Sheet metal, 2' x 2', 22 ga $18 (ended up not using this)

Relays/Wire/fuses $15

Switch/diode/resistor $6

--------------------------------------------

Total $216 ($198 without the sheetmetal)


You could easily have done this cheaper if, for example, you got a smaller fan, or used a Taurus fan, etc. I actually bought a junkyard Taurus fan for $23, but that thing was so huge I didn't even want to mess with it.

Now that both fans operate simultaneously, and the fan is mounted up close to the core, cooling happens almost instantly. If the fans are turned on as the temp is reaching 220*F, it will drop to under 200*F in a matter of 3-4 minutes. I consider this an overwhelming success.

 

[wim hoppenbrouwers]

Hallo. A very nice job and a good presentation. :cheers::thumbup:

 

[bluejeepkid]

good kob except it appears that your water pump is turning the wrong way..

 

[lost honda pro]

Hallo. A very nice job and a good presentation. :cheers::thumbup:

Thanks!

good kob except it appears that your water pump is turning the wrong way..

Thanks, but it's right. See the first pic in this thread.

 

[stumpXJ]

good kob except it appears that your water pump is turning the wrong way..

Did you see the pictures? Its going the same way it would as stock.

Great job, and a very nice write up!

~James

 

[dunbad]

Even i could follow those instructions. Maybe its time to crack open the wallet and become a paid up member after reading posts like that!!!

well done, and thanks for including the problems you come across and how you got round them

 

[Mullet Man]

kewl.

why did you add an idler, when in some of the other writeups they reuse the stock belt?

 

[Red90Laredo]

how is that supposed to cool effectively with no shroud? not bashing your work but I would want at least the same cooling capacity as the mechanical fan.

 

[lost honda pro]

kewl.

why did you add an idler, when in some of the other writeups they reuse the stock belt?

I added an idler because with the 97+ XJs, you can't re-route the belt correctly after removing the mechanical fan pulley - you need to add a pulley to remove one. And I did re-use the OE belt, it fits perfectly.

how is that supposed to cool effectively with no shroud? not bashing your work but I would want at least the same cooling capacity as the mechanical fan.

Because the fan is so close to the core (~0.5") it pulls the vast majority of the air through the core. Here's how I figured it:

- without the shroud, I'm probably getting around 75% of my air through the core, which is still ~2200 CFM (just the main fan)

- this fan runs with the OE auxiliary fan all the time, so I'm also getting ~1000 CFM from that fan =~3200 CFM

- as it was originally, the mechanical fan at idle couldn't have pulled more than ~2000 CFM (probably more like 1500), so I'm running well above that, at least in theory

I see your concern, and I am planning on adding some shrouding, but I wanted to get it working for the time being. As it sits, both fans provide ample cooling for any situation I could get in.

 

[Red90Laredo]

you are probably right- I just wanted to bring it to your attention.

I had a project car many moons ago and could not figure out why it kept getting hot- took my uncle ten seconds to tell me- "hey man, there is no shroud on this thing"

 

[lost honda pro]

you are probably right- I just wanted to bring it to your attention.

I had a project car many moons ago and could not figure out why it kept getting hot- took my uncle ten seconds to tell me- "hey man, there is no shroud on this thing"

Thanks, I definitely considered it though. The shroud I made probably could have been modified, but being that the fan was sitting so high up (almost into the hood) I scrapped that idea and went with the current setup.

Like I said, I'm gonna try and get a shroud on it, but for the time being, it's working ok.

Thanks again for the heads up, and I'll update if/when I get a shroud on it.

 

[chpmnsws6]

Your not worried about it getting to hot at 228 before the fans kick on? They make adjustable thermostats for electric fans

 

[techno1154]

Great job. atriot:

X2 on the fan shroud. It will not only help to direct air flow through the radiator but will prevent human body parts from coming in contact with the metal fan blades.

 

[lost honda pro]

Your not worried about it getting to hot at 228 before the fans kick on? They make adjustable thermostats for electric fans

The ECM kicks the fans on at 218*F IIRC, and I do want something to manage the temp better, just haven't found it yet.

I'm trying to make a circuit that reads off the OE temp sensor and uses it's resistances to operate the fans.



Thanks for all the responses!

 

[dunbad]

Yeah i noticed the fan shroud thing, but some companys claim that they are not effective at assissting with cooling??!! The company that makes those triple fan things for example just have a protective grill type set up over the blades of the fans. I cant recall the reason they gave for shrouds being inefficient but its what they claim. (if i recall correctly i think they mentioned drag)

Also have you seen the write up 110 Flex-a-lite install?
that guy got a control box fitted where he can adjust the temp, maybe worth a look if you havent seen it already.

 

[Yamayama]

Haven't really looked too heavily into this, but this is all things that are at least theoretically very inline with the Computer case fan-modding range for electronics. I've actually used such components for cooling stereo amp racks before. Temperature-senstive switches, aux readouts, and multiple fan controls with all sorts of options for variable speed/ manual override, etc... Best thing, they're all designed to work off of 12v... the variable speed bits might be tricky as I doubt any of them would be up to handling the amperage a fan of this scale requires, but if it's an on/off situation hookedup to a termometer with a thermostat-type control to it, relays are our friends...
I'm a bit busy to do the full research on it at the moment, and I'm sure it's been atleast pondered by others before, but here's the general types of things I'm talking about...
http://www.newegg.com/Store/SubCategory.aspx?SubCategory=11&name=Controller-Panels