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  #241  
Old April 7th, 2018, 16:45
srb531 srb531 is offline
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Re: Radiator Fan Override Switch (The Easy Way)

nothing about this sounds easy, unless you are experienced w/ auto electrical / computer systems. just my take on it.
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  #242  
Old July 19th, 2018, 08:49
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srmitchell srmitchell is offline
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Re: Radiator Fan Override Switch (The Easy Way)

Quote:
Originally Posted by weaselguys View Post
I just finished doing this on my 01 XJ at first it only half worked and I got a cel ,first I found the db/pk in the large loom and confirmed it was pin 2 on con 3 at the PCM , I cut it and ran both wires to the relay as per instructions , I then looked for the db/w wire my large loom only had 1 , I spliced into it , connected the ground & hooked up a switch and checked all connections. My fan came on when I activated the switch no cel , it came on at the right temp but when I tried it with the AC it would not come on and I got the cel. I looked back thru the instructions and saw the pic of the small loom and db/w wire.This is the loom that connects to con 1 on my 01 , I swapped connections to this wire and now everything works correctly and no cel. Thanks to the OP for this mod.
Just followed this mod to the letter, and I got a CEL. 2001. Using the BL/WT wire from C3. The fan works but I got a cel once warm. Can anyone confirm that switching to the BL/WT wire from C1 will fix it?
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  #243  
Old July 19th, 2018, 09:01
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Mudderoy Mudderoy is offline
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Re: Radiator Fan Override Switch (The Easy Way)

Quote:
Originally Posted by srmitchell View Post
Just followed this mod to the letter, and I got a CEL. 2001. Using the BL/WT wire from C3. The fan works but I got a cel once warm. Can anyone confirm that switching to the BL/WT wire from C1 will fix it?
Check this and see if it is different. I may not have updated it on this site.

http://www.xjtalk.com/showthread.php...verride-Switch
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  #244  
Old July 21st, 2018, 08:17
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srmitchell srmitchell is offline
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Re: Radiator Fan Override Switch (The Easy Way)

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Originally Posted by Mudderoy View Post
Check this and see if it is different. I may not have updated it on this site.

http://www.xjtalk.com/showthread.php...verride-Switch
Thanks man. I was able to figure it out.

I had two wires, a blue one and a teal one, both spliced into the factory Blue/Pink trigger. One went to the PDC, one to the PCM. Turns out I had my switched ground spliced into the PCM side. It still worked, but once at operating temp, it threw the CEL.
Switched the grounded switch wire to the PDC side, and it seems to work no issues.

Thanks for this mod! About 9 years ago, I wired a fan switch, and it simply had a relay and a spliced wire to the fan harness. It stopped worked recently, and I found blackened insulation near my splice. Fixed that, redid all the wiring and it seems much better.
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  #245  
Old October 10th, 2018, 19:08
Goot449 Goot449 is offline
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Re: Radiator Fan Override Switch (The Easy Way)

I followed these instructions and it worked very well on my 99 XJ, but for some reason ever since installing this relay, I am blowing O2 heater fuses. I have triple checked everything with a multimeter, drawn schematics of how everything plays out, but for some reason I cannot figure out what could possibly be causing this to happen. Has this happened to anyone else?

I am certain this is the cause, as when I remove the relay I added, I stop blowing 02 heater fuses, but when I put the new relay back, they blow again.
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  #246  
Old October 14th, 2018, 20:50
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chasdb chasdb is offline
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Re: Radiator Fan Override Switch (The Easy Way)

Quote:
Originally Posted by Goot449 View Post
I followed these instructions and it worked very well on my 99 XJ, but for some reason ever since installing this relay, I am blowing O2 heater fuses. I have triple checked everything with a multimeter, drawn schematics of how everything plays out, but for some reason I cannot figure out what could possibly be causing this to happen. Has this happened to anyone else?

I am certain this is the cause, as when I remove the relay I added, I stop blowing 02 heater fuses, but when I put the new relay back, they blow again.
Are you getting your start/ run power from the O2 heater fuse? Is your relay equipped with a diode on the coil to suppress noise? If so you way have your wires swapped on your coil, pins 85 and 86 on your relay.
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  #247  
Old August 8th, 2019, 15:00
SByota SByota is offline
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Re: Radiator Fan Override Switch (The Easy Way)

Got this all hooked up today on my 97. Followed the diagram in the original post exactly. Started the engine and flipped the switch, fan came right on. Turned my A/C on, no fan. AC clutch engaged and air was definitely working. No check engine light. Any ideas?
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  #248  
Old August 11th, 2019, 21:23
fyrfytr1717 fyrfytr1717 is offline
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Re: Radiator Fan Override Switch (The Easy Way)

How long did you let it run for? The fan doesn't just automatically turn on with the A/C, rather it cycles on and off occasionally while you're using it.
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  #249  
Old August 11th, 2019, 21:49
SByota SByota is offline
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Re: Radiator Fan Override Switch (The Easy Way)

Quote:
Originally Posted by fyrfytr1717 View Post
How long did you let it run for? The fan doesn't just automatically turn on with the A/C, rather it cycles on and off occasionally while you're using it.
I let it get to operating temperature (200ish) idling in the driveway. No electric fan at all, expect when I flipped the new switch.

I took it for a 20 min drive with the A/C on, up some hills and put some heat into it. I got it to 210, but again, no fan without the switch. Iím thinking itís normal, but just wanted to see if anyone else had a similar problem.

Thanks for the great write up.
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  #250  
Old August 14th, 2019, 12:15
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kastein kastein is offline
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Re: Radiator Fan Override Switch (The Easy Way)

That's pretty normal. If you wanted to truly test it, you could unplug the CTS, if the fan comes on immediately, the ECU's relay control output is working correctly and it just didn't want the fan on for some reason. This will result in you getting a DTC for a circuit fault on the CTS that you can either clear or let disappear on its own, so don't do it if you have an emissions test coming up.
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  #251  
Old August 14th, 2019, 19:09
SByota SByota is offline
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Re: Radiator Fan Override Switch (The Easy Way)

Quote:
Originally Posted by kastein View Post
That's pretty normal. If you wanted to truly test it, you could unplug the CTS, if the fan comes on immediately, the ECU's relay control output is working correctly and it just didn't want the fan on for some reason. This will result in you getting a DTC for a circuit fault on the CTS that you can either clear or let disappear on its own, so don't do it if you have an emissions test coming up.
CTS is the temperature sensor in the thermostat? Unplug while running and the fan should come on immediately? I have a scanner and have zero issues clearing codes. Smog not due for another year. Thanks.
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  #252  
Old August 16th, 2019, 10:32
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kastein kastein is offline
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Re: Radiator Fan Override Switch (The Easy Way)

Correct. The 97-01s use that sensor for ECU fuelling strategy, gauge readout data, and fan control choices. If you unplug it, it detects the fault and assumes the worst and turns the fan on, so it's an excellent first step in diagnosing electric fan issues on 97+. Only downside is the codes it'll set but that doesn't sound like a problem for you.
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Definitely do not hunt down my phone number at 3AM, text me about it, and then threaten violence when I am not helpful. It will not get you what you want.
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  #253  
Old August 16th, 2019, 17:27
Sumo2014 Sumo2014 is offline
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Re: Radiator Fan Override Switch (The Easy Way)

I ran across this thread a few days ago and been trying to figure it out. I am new to the jeep world bought a 2001 XJ couple months ago. It does run a little bit hot so I was looking for ideas and I ran across this. I have no electrical experience. So I am a little bit confused with this thread now I have been told that the schematic here it is for a 1999 and that so I am a little bit confused with this thread now I have been told that the schematic here is for a 1999 and that the 2000 and 2001 is different. I haven’t been able to figure out the difference. does anyone have an updated schematic or detailed instructions to the difference? Any help or can point me into the right direction would be Any help or can point me in the right direction. It would be very much appreciated
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  #254  
Old August 29th, 2019, 21:53
Kidd XJ Kidd XJ is offline
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Re: Radiator Fan Override Switch (The Easy Way)

Being that this thread is still going I have a question/suggestion.
Has anyone ever tried just using a DPDT (double pole/double throw) switch?


Run fan wires to center pole



run computer to one side (top pole)



run fused hot to other (bottom pole)



Theoretically in center position fan will be off
bottom position fan will run through computer
top position fan will be on


Just curious if anyone has tried this or if anyone has an opinion???
This is how I was thinking of wiring my fan.
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  #255  
Old October 3rd, 2019, 20:56
SByota SByota is offline
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Re: Radiator Fan Override Switch (The Easy Way)

Quote:
Originally Posted by SByota View Post
I let it get to operating temperature (200ish) idling in the driveway. No electric fan at all, expect when I flipped the new switch.

I took it for a 20 min drive with the A/C on, up some hills and put some heat into it. I got it to 210, but again, no fan without the switch. Iím thinking itís normal, but just wanted to see if anyone else had a similar problem.

Thanks for the great write up.
So I dug into this further today. My electric fan has not come on once on itís own since I installed the relay/overide switch. I suspected the blue/white 12v wire I used as a power source. I checked the wire again, 12v with the key on, but 0v once the engine was running. I used another known switched 12v source, the cigarette lighter, and it works perfect now. Fan comes on as soon as any AC or defrost is selected. Switch still works perfect.
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