Hi guys
With inspiration and advice from from forum members GoJeep, Billnick, junglejuice and others, I have finally completed the wiring diagram I will be using for the dual electric fan conversion in our XJ Cherokee. This has been covered a number of times, however it has been difficult to find a full wiring diagram (thanks Billnick for your work so far), and nothing which integrated a trigger for trans fluid temp. This writeup will be for the Australian delivered XJ Cherokee 4.0L Auto, but may apply to other models, Jeep or otherwise.
So I thought I'd document the install here to share with any others who may benefit.
Key goals I seek by this conversion (in no particular order) are:
- lower cost of replacement than belt-driven fan clutch
- improved power
- improved engine response
- improved fuel economy
- lower noise levels
- improved cooling efficiency
- better management of transmission fluid temp while using stock (Aussie RHD) trans cooler setup
Parts I'll be using:
- 16" 3300CFM thermo fan from eBay member dizzy-su
- new drive belt 6PK2310 from Repco (but will likely be cheaper from Rock Auto if buying other items)
- 40 amp relays with interlocking bases from eBay
- 40 amp fuses with water resistant covers from eBay
- appropriate gauge wiring
- Derale 13021 inline trans fluid fan thermostat from Summit Racing (180*F on, 175*F off - 3/8" fittings)
- rocker switches with LEDs from Supercheap Auto / eBay
- LED indicator light from eBay
I will be completing this in stages, with the majority of work to be carried out first, followed by trans temp and "Fans off" kill switch for water crossings and diagnosis.
Please note I do not take any responsibility for your actions based on the information provided here. This is posted for information purposes only, and your results may vary.
Also please note that if your engine mounts are not in good condition it can make for mounting your new fan near-impossible. I found this out the hard way and once I replaced my left engine mount I could finish this up in no time.
Billnick suggested to use a three-pole relay, however I will be using standalone relays with inter-locking bases for ease of replacement and cost. It also has the option for a third fan, for those who would like to run triple radiator fans, but I will be simply replacing the XJ's belt-driven fan with a 16" thermo fan, and continuing to use the factory 10" fan.
EDIT - I have summarised all stages I completed into this first post to make it easier to navigate.
Stage 1 - Wiring Loom
With thanks to JungleJuice I created a wiring loom from his diagram. As the diagram he provided shows the circuits themselves, I used this to work out the pins for the relays and how to solder the wiring.
Below is a simple diagram to show how to solder your loom. I have modified this slightly from my original photos due to a simple error I had made initially and a simplification for the layout. Please note light grey is white.
I grouped the wires and labeled them.
Then I used a cable tie to keep the wires I was soldering from moving, which I removed after heat shrinking the solders.
Then I measured the lengths of the wires to the fans and battery as required from the point I chose to mount the relays (alongside the factory fuse/relay box in the engine bay), and soldered/heat shrinked these to the loom. I then added the ring fittings to the ends.
Stage 2 - Fitting the new thermofan
After removing the drive belt, undoing the top bolts of the fan shroud and undoing the clutch fan and pulley, I removed the fan and shroud as one piece. I also removed and set aside the power steering pump to allow this.
Once the shroud was out, I sized up the new thermofan to the shroud. As expected from Go Jeep's write up, the new thermofan was a few mm too wide for the shroud. Essentially, I needed to remove the entire flange of the thermofan and leave it as smooth and flat as possible to get it to fit. I used a sanding disc on an angle grinder to do this as it was relatively effortless.
Now that the thermofan will fit in the shroud I set about pop-riveting it to the shroud. Now the pop rivets I had were a little short but I didn't feel like heading out to get more, so I used a couple of cable ties to hold them in tight enough for the rivets to hold. The cable ties must be removed prior to refitting the shroud. If you use rivets which are at least about 12mm deep this shouldn't be an issue.
Now came the removal of the existing mount and bearing. In Go Jeep's writeup he removed the clutch fan mount and pressed the bearing out - which was a luxury I couldn't afford with what I had available to me. So in the end the most effective way for me to complete this was to use an angle grinder with stainless steel cutting discs. A hack saw just wouldn't get through the bearing.
Now as you can see, the cutting disc couldn't get deep enough to get through. So what I had to do was cut a section from the front wheel and get through it at an angle. This was enough to clear the motor of the thermofan (once I had sorted out the engine mount). If I get time one day I may finish the cut straight, but it's not doing any harm there.
When refitting the power steering pump, I needed to remove a couple of the plastic bars from the back of the thermofan in order to get the bolts into their respective holes. If you trim the top of the fan shroud to match the depth of the thermofan this will also make this job easier, but I put up with it to keep it looking neater in the engine bay.
(Awaiting image)
Now the new route of the belt just touches the head of a bolt, and this needs trimming back a couple of mm. The belt tensioner on the alternator mount (on my RHD MY98 XJ) needs to be tightened out quite far towards the end to clear a bolt below it - you should be able to twist the belt to no more than 90* at the long, top section.
Stage 3 - Switches
I looked at the OEM relay for the thermofan and deduced that (on my MY98 XJ) the wire for activating the factory fan was light blue, so I tapped this for switching on high speed mode at the factory settings (105*C and with Air Conditioning). I left some extra wire inside the fuse box with heat shrink on the end for when I wire up a manual switch and/or a thermostat on the outlet line of the trans cooler.
I also used a wire I had in place from a fused ignition source in the interior fuse panel to switch on low speed with ignition (dark blue in this photo).
I mounted the relays on the engine side of the fuse/relay box with cable ties.
(Awaiting image)
I'll update this when I add the additional switches down the track (possibly this summer), but for now this is where I will leave it.
Results
No scientific results, however it has indeed been keeping its cool with mainly the low speed and the high speed fan kicking in from the PCM every so often. On the highway in cooler temps such as the blue mountains, you can tell the temp is being kept low enough to bump the ceiling of the thermostat - just as intended.
As expected, engine revs more freely, much quieter operation, noticeably smoother gear shifts and a little more top end power. Quite happy at this point - but will be happier with a thermostat for the transmission with my stock setup for completely automated operation.