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  #181  
Old July 8th, 2014, 13:06
PocketsEmpty's Avatar
PocketsEmpty PocketsEmpty is offline
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Re: Radiator Fan Override Switch (The Easy Way)

Update: PCM isn't turning on the E-fan either. Could this be caused by weak voltage in the blue/white wire ST-RUN source in the big loom? I saw some replies referencing the one in the smaller loom correcting their problem. I'll check things out with the multimeter later and hope to get to the bottom of this.
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  #182  
Old July 9th, 2014, 10:56
fyrfytr1717 fyrfytr1717 is offline
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Re: Radiator Fan Override Switch (The Easy Way)

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Originally Posted by PocketsEmpty View Post
BUT...per beasticles' diagram, Pin 30 and 87 are actually switched around. You confirmed this is correct. Is this mixed up in your original post? Perhaps all I need to do is switch those around? I currently have the DB/PK wire + switch ground spliced to 87. The fan does switch on and no CEL when I do turn the switch to ON.
Honestly, it doesn't matter. The relay is just making and breaking the connection between the ground and the factory relay. It doesn't care what's connected to either end. If this was a more complex circuit where you were using both the 87 & 87a pins, then it could matter. Beasticles labeled it correctly per the way I drew it, but now that you've pointed it out, I see that my drawing doesn't exactly match the directions. I just cut and pasted the relay symbol from the FSM. Relays are typically drawn with the 12V+ connected to the COM terminal and the device being activated connected to either the NC or NO terminal. I guess I should have flip-flopped the switch symbol inside the new relay since we are switching a ground.

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Originally Posted by PocketsEmpty View Post
Update: PCM isn't turning on the E-fan either. Could this be caused by weak voltage in the blue/white wire ST-RUN source in the big loom? I saw some replies referencing the one in the smaller loom correcting their problem. I'll check things out with the multimeter later and hope to get to the bottom of this.
Think you're on the right track here. It seems as if the coil isn't being energized in your new relay which would indicate either a bad connection somewhere between the PCM and Pin 85, or (more likely) insufficient voltage being supplied to Pin 86. Test that DB/WT wire and make sure it's giving you 12V+. The relay needs at least 8V to activate.

You could also try disconnecting the PCM from Pin 85 and applying a ground directly to the pin. You should hear the new relay "click" if it has the necessary voltage and is activating properly.
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  #183  
Old July 9th, 2014, 11:49
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Re: Radiator Fan Override Switch (The Easy Way)

Thanks for the reply! I will do exactly that.
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  #184  
Old July 10th, 2014, 10:43
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Re: Radiator Fan Override Switch (The Easy Way)

Minor point - you don't actually need to disconnect the ECU from that pin to do that test. That pin contains what's technically known as a ground-side switch, grounding the wire with the ECU still connected won't break anything, though it may cause a DTC for a shorted or inoperative fan relay circuit. Unplugging the relay or interrupting that wire with the jeep turned on will result in a similar code of some sort anyways, so you aren't going to really lose anything either way.
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  #185  
Old July 11th, 2014, 19:42
DanMan2k06 DanMan2k06 is offline
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Re: Radiator Fan Override Switch (The Easy Way)

Edit: I'm a dunce.
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  #186  
Old July 12th, 2014, 00:10
fyrfytr1717 fyrfytr1717 is offline
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Re: Radiator Fan Override Switch (The Easy Way)

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Originally Posted by kastein View Post
Minor point - you don't actually need to disconnect the ECU from that pin to do that test. That pin contains what's technically known as a ground-side switch, grounding the wire with the ECU still connected won't break anything, though it may cause a DTC for a shorted or inoperative fan relay circuit. Unplugging the relay or interrupting that wire with the jeep turned on will result in a similar code of some sort anyways, so you aren't going to really lose anything either way.
Good info! Wasn't sure what would happen, just thought it might not be good. Thanks for the technical explanation.
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  #187  
Old July 12th, 2014, 13:36
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Re: Radiator Fan Override Switch (The Easy Way)

Okay guys I got this fixed the other day and wanted to update. When I tested the blue/white wire out of the big loom, it had a solid 12.4 volts with the ignition in the RUN position. Pretty interesting. But when I ran a jumper wire direct from the battery to pin 86, it worked perfectly. I then cut into the smaller loom and found that blue/white wire and hooked it up, and it works great now. Thanks for the help, fantastic mod!
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  #188  
Old July 28th, 2014, 18:53
lowNslow lowNslow is offline
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Re: Radiator Fan Override Switch (The Easy Way)

Just did this mod today and all was good except the fan wouldn't come on with the ac. Turns out the dark blue/Wht wire I spliced into goes completely dead as soon as the ac is activated.

Took an annoying amount of time to troubleshoot. Still not sure what that wire runs.
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  #189  
Old August 23rd, 2014, 20:05
beasticles beasticles is offline
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Re: Radiator Fan Override Switch (The Easy Way)

Fyrfytr thank you again. I wired this up today and it worked like a charm...until I switched on the AC. Triggered the CEL immediately. I see on page 11 of this thread someone posted about putting a resistor in the switched line. You didn't run into this problem yourself? I followed the diagram I supplemented with relay pin numbers to a tee. Any thoughts would be much appreciated.
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  #190  
Old August 23rd, 2014, 20:32
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Re: Radiator Fan Override Switch (The Easy Way)

Reading some of the replies, it looks like a great idea to leave well enough alone and let the Jeep operate as the factory intended.
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  #191  
Old August 23rd, 2014, 21:43
beasticles beasticles is offline
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Re: Radiator Fan Override Switch (The Easy Way)

I found this guy who was having a similar issue and he skipped the DB/WT switched wire and connected straight to the positive terminal of the battery:

I disconnected the positive going to the relay and connected it directly to the battery positive. The "CHECK ENGINE" has gone out. I suspected the PCM didn't like the 12 volts coming and going. If it stays off for the next few days, a week, I'll report back and probably create a new thread on how to install a electric fan on 1997+ XJ bypass switch
http://naxja.org/forum/showthread.php?t=1025399

I'll give it a go and report back
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  #192  
Old August 24th, 2014, 11:41
beasticles beasticles is offline
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Re: Radiator Fan Override Switch (The Easy Way)

This worked to cure the CEL for me! Ran a lime direct to positive battery terminal instead of tapping into DB/WT wire like I had it. Now no CEL is triggered with AC on and the fan switch works great. Thanks fyrfytr!

This worked on a 2000 XJ so I assume this is the trick for '00 and '01 model years.
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  #193  
Old August 24th, 2014, 16:17
beasticles beasticles is offline
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Re: Radiator Fan Override Switch (The Easy Way)

And by a lime* I meant line*
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  #194  
Old August 24th, 2014, 22:30
fyrfytr1717 fyrfytr1717 is offline
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Re: Radiator Fan Override Switch (The Easy Way)

Quote:
Originally Posted by yossarian19 View Post
Reading some of the replies, it looks like a great idea to leave well enough alone and let the Jeep operate as the factory intended.
No one is going to make you do it to your Jeep, but judging by the fact that this thread is 13 pages long and has over 33,500 views... I think there's some interest in doing this mod.
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  #195  
Old August 24th, 2014, 22:35
fyrfytr1717 fyrfytr1717 is offline
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Re: Radiator Fan Override Switch (The Easy Way)

Quote:
Originally Posted by beasticles View Post
This worked to cure the CEL for me! Ran a lime direct to positive battery terminal instead of tapping into DB/WT wire like I had it. Now no CEL is triggered with AC on and the fan switch works great. Thanks fyrfytr!

This worked on a 2000 XJ so I assume this is the trick for '00 and '01 model years.
Glad you got it figured out. I'm not sure if there is a variance with the '00 & '01 models (very well may be), but I know that it seems finding the correct switched ignition wire seems to be the trickiest part of this mod. The DB/WT in the small loom seems to be a more reliable choice than hoping you get the right one in the big loom. That being said, there's no major issue with running it directly to the battery, you just have to remember to turn it off.
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