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Electric fan switch

T3hk1w1

T3hk1w1

NAXJA Forum User
Location
Houston
I'm getting tired of the whole overheating at low speeds thing(yesterday's high was 101?F, which doesn't help), so I've decided to install a manual switch to turn on my OEM aux electric fan. I've found a few old threads related to this topic, such as http://www.naxja.org/forum/showthread.php?t=9546&highlight=switch+conversion+fan , but I'm afraid I'm not yet knowledgable enough to figure it out from that. Specifically, I have a 2-position rocker switch(30AMP, 3 prong w/an LED) that I want to install that will turn on the electric fan, without disabling the temp activation or the A/C activation features of the fan. My XJ is a 2000 Sport model with an auto trans and the 4.0L. I've located both a relay and a fuse for the cooling fan in the fuse box(is that what you guys refer to as the PCM?) but I'm not sure how to wire it up. I apologize for asking what seems to have already been answered, but my knowledge of electrical systems is limited-can someone walk me through it?
 
How good are you at splicing wires?
If you feel pretty electrically inclined you can run a positive wire inside your cab off the battery to the switch inside on the top prong and have a wire running out of the bottom prong to the aux fan wires after the fuse. The middle prong is a ground so connect it somewhere, because that will be responsible for lighting up the LED.
 
Run the power lead directly off of the battery? Should I run a fuse with that line so it won't blow the fan motor? What do you mean by after the fuse? Between the fan and the fusebox, or do the wires leave the box again through the same loom? Also(last question), which wire should I splice into? There are 2 wires, a black one and a blue one, same guage.
 
I switch-wired my electric fan, bypassing the sensor completely. Run a 30 amp inline fuse from battery to switch, then route the wire from switch to fan motor. The only drawback is you have to remember to turn it on when the ambient temp is around 65 or above or when pulling a pass.
 
Around 65 or above..if you mean farenheit, then I might as well just leave it on whenever the engine is running...
 
T3hk1w1 said:
Around 65 or above..if you mean farenheit, then I might as well just leave it on whenever the engine is running...
Click to expand...
Yeah, it's only 65 or above about half the year around here. Just make it part of your driving ritual, fire up engine, turn fan switch on five minutes later.
 
Our outside temp is currently 94 degrees...
 
Yep the power off the battery is 12+Volts and that is what the fan requires to run. You can stick a 30Amp fuse along the line anywhere you choose before the switch.
You said that you wanted the fan to be able still do its fuctions like run when A/C is on and stuff so if you do it after the fuse along the wiring harness that goes into the fan your good, but if you do it beofre the fan than you control the flow of power to activate the functions that are normally carried out. If you open the hood of your Jeep look at the wires going into the fan and follow them along there should be a fuse somewhere there so the Jeep can tell the fans when to activate. Those are the wires you want to tap into. Now if you want your fans always on just tap the wire coming into the ballist resistor. The one closets to the master cylinder is the one you want.
 
So the wires going into the fan are the ones I want to tap into if I don't want to affect normal function of the fan. Any idea which of the two wires gcoming from the fan I should splice into? one is black and the other is blue. By the way, there is a diagram on the back of my switch that shows the top, middle, and bottom prongs as being "Earth", "Load", and "Supply", respectively. Does that mean the bottom prong is where I should run my power lead?
 
The black one is your ground and the blue one is the positive lead into.
Tap into the blue wire with the power from switch.
 
Gotcha. I actually just made the interesting discovery that turning on my A/C does not turn on the fan...I checked the fan motor via jumpers to the battery and it works. So...since my factory wiring is apparently being a nonparticipant already, I think I may just disconnect the fan from the factory loom, run the black wire straight to ground, and run the blue wire to the battery via the switch and an in-line fuse. Would it be a problem to leave the factory loom disconnected? (I noticed there are already 2 unused connectors like this-one is for fog lights and the other is for ???)
 
Nope you can disconnect it. Hook a wire onto your ballist resistor and when you turn your key on the fan will turn on and when you shut the motor off so will the fan.
 
Befor you burn switch after switch up.. This is amuch safer wiring if you really want to put a manual switch on it. It will not heat the switch up, just do not forget to add a fuse inline of the 12 volt power..
relay2.jpg
 
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Is that a standard 4-pin relay?
Is the wire you have going into 85 spliced off of the wire going into 30?
EDIT: the fan did come on when I disconnected the temp sensor, so it seems that works.
 
Last edited:
You can either use a 4 or 5 prong. If you use the 5 you just do not use the center pin. I seem to find the 5 pins more often so I use those all the time, and are cheaper then the 4 pins for some reason.More common I guess.
 
So you have (12V power supply) -> (fuse) -> (splice) -> first wire going to "30" and the spliced wire going to "85" Is that correct?
 
Yup that sounds about right. I usually just splice one to the other (30 + 85) close to the relay. Less wires that way.
 
Well, I went ahead and started the install. I have all of the underhood wiring done, I just need to wire the switch now. Any suggestions on where to place the switch? Everything works correctly, switch wire turns on the fan when I ground it. The check engine light is now on however, probably from my messing with misc stuff in the engine bay :doh:
Install pics below :)

Fuse wired to the power lead

DSC00646.jpg


Relay (Bolted to body)

DSC00647.jpg


Connection to stock wiring circuit (I spliced it into the stock loom rather than disconnect the existing loom)

DSC00649.jpg


Gratituous Cherokee pic :) (that's one of our camp's dog trucks in the background)

DSC00650.jpg
 
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