electric fan switch mod?

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Aug 16, 2013 | 06:10 AM

#16

XJwonders

CF Veteran

Joined: Jan 2013

Posts: 19,219

Likes: 45

From: west chester, pa

Year: 1999

Engine: 4.0

Quote:

Originally Posted by Jamison

Yes, it will work on SOME XJs. Not on mine. The fan runs fine until you switch on the A/C and it trips a CEL every time. Diode or no diode, I get a CEL. It took me no longer to run my relay than it did for you to dig out the correct pink/blue wire. Same time to run the switch. To each his own. I tried the "trick the PCM route" with the pink/blue wire to ground. My Jeep didn't like it, so I just wired in a switch and now I can run the fan anytime I want and it still comes on with the A/C when its supposed to and also when the temp reaches 218, even if my switch is off.

It doesn't trigger a CEL on when I turn the ac on. It only trigger the CEL when I turn the fan on manually. And the CEL go away after few more starts.

Aug 17, 2013 | 08:20 AM

#17

94XjSport94

CF Veteran

Joined: Apr 2011

Posts: 14,553

Likes: 1

From: Carrollton, GA

Year: 1994

Model: Cherokee

Engine: Inline 6 4.0L High Output

Well I don't have a problem with how mine is so I'll keep doing it my way.

Aug 17, 2013 | 08:50 AM

#18

XJwonders

CF Veteran

Joined: Jan 2013

Posts: 19,219

Likes: 45

From: west chester, pa

Year: 1999

Engine: 4.0

Quote:

Originally Posted by 94XjSport94

Well I don't have a problem with how mine is so I'll keep doing it my way.

Exactly I don't have a problem with mine either!

Aug 17, 2013 | 10:15 AM

#19

evan00xj

Seasoned Member

Joined: Sep 2012

Posts: 461

Likes: 0

From: charlotte

Year: 2000

Model: Cherokee

Engine: 4.6L stroker

Quote:

Originally Posted by XJwonders

Exactly I don't have a problem with mine either!

Got the Same setup no problems here on my hypersensitive 2000 xj

Aug 25, 2013 | 06:34 PM

#20

BrewinXJ

Junior Member

Joined: Aug 2013

Posts: 34

Likes: 0

From: Las Vegas

Year: 1998

Model: Cherokee

Quote:

Originally Posted by Jamison

Can you provide a diagram of what type of switch and relay you used? And how you wired it in? I like the idea of this but I don't understand it 100%. PIcs would even be better.

Sep 2, 2013 | 01:21 AM

#21

Turbocube

Member

Joined: Jun 2013

Posts: 149

Likes: 0

From: Orlando, Florida

Year: 1995

Model: Cherokee

Engine: 4.0L

I'd also love to see a diagram for Jamison's design. As I have a '95 it might be my best bet.

Thanks in advance.

Apr 4, 2016 | 09:39 PM

#22

IJM

CF Veteran

Joined: Jan 2014

Posts: 1,539

Likes: 351

From: District of Columbia

Year: 1998

Model: Cherokee (XJ)

Engine: 4.0

Quote:

Originally Posted by Jamison

I'm still not sure why you guys screw around with trying to trick the PCM and tripping CELs and stuff.
Its simple...
Get a switch and relay. Wire the switch to trip the relay and splice it in to the hot wire on the fan right at the fan itself. The PCM will still work to turn it on when it is hot or the ac requires, but your switch will allow you to run the fan when you want. If you power the switch to trip the relay with a "always hot" wire, you can run the fan with the engine off for a few minutes to keep air flowing over the motor. Works great with hood vents.
If you power the switch with an ignition controlled power source, you wont have to worry about forgetting to turn it off.
This works with ALL model years and I have yet to see it trigger a CEl.

LEAVE the PCM ALONE!

Pardon me for asking a stupid question, but is there a concern about having two 12v sources going to the fan at the same time when the switch is on also with the A/C or 218*+? Does this double the voltage, or is it not an issue? With the hot weather approaching, I'd like to wire up my aux fan switch, and I don't want to mess with CELs and that sort of thing.

May 23, 2016 | 09:24 PM

#23

IJM

CF Veteran

Joined: Jan 2014

Posts: 1,539

Likes: 351

From: District of Columbia

Year: 1998

Model: Cherokee (XJ)

Engine: 4.0

^^^ Any insight to my question above?

May 24, 2016 | 01:45 AM

#24

Veeb0rg

::CF Moderator::

Joined: Sep 2009

Posts: 3,495

Likes: 482

From: Glen Burnie, MD

Year: 2001

Model: Cherokee (XJ)

Engine: 4.0l

Won't double the voltage. Won't be an issue.

May 24, 2016 | 05:35 AM

#25

SteveMongr

Beach Bum

Joined: Jul 2011

Posts: 6,123

Likes: 22

From: Cape Hatteras, North Carolina

Year: 2000 WJ

Model: Grand Cherokee

Engine: 4.0

Quote:

Originally Posted by Jamison

I tried the "trick the PCM route" with the pink/blue wire to ground. My Jeep didn't like it, so I just wired in a switch and now I can run the fan anytime I want and it still comes on with the A/C when its supposed to and also when the temp reaches 218, even if my switch is off.

Quote:

Originally Posted by Jamison

If you power the switch to trip the relay with a "always hot" wire, you can run the fan with the engine off for a few minutes to keep air flowing over the motor. Works great with hood vents.
If you power the switch with an ignition controlled power source, you wont have to worry about forgetting to turn it off.
This works with ALL model years and I have yet to see it trigger a CEl.

Same exact functions as installing a switch on ground wire. I sometimes use the fan with engine off, it is ignition controlled.

Nov 11, 2016 | 10:03 PM

#26

mmorris

Junior Member

Joined: Jun 2013

Posts: 59

Likes: 0

From: NE Missouri

Model: Cherokee

Jamison,
"My Jeep didn't like it, so I just wired in a switch and now I can run the fan anytime I want and it still comes on with the A/C when its supposed to and also when the temp reaches 218, even if my switch is off."

Could you help me with the fan switch mod you did on your 2000? Being a novice mechanic, I could really use some specific instructions on how to do this. I'm having the heat soak/vapor lock problem and need some circulating air to cool under the hood. Thanks in advance!

Nov 12, 2016 | 05:18 PM

#27

BlueRidgeMark

CF Veteran

Joined: May 2012

Posts: 7,965

Likes: 964

From: Lost in the wilds of Virginia

Year: 1998 Classic (I'll get it running soon....) and 02 Grand

Model: Cherokee (XJ)

Engine: 4.0

If you are not isolating the existing circuit with either a relay (preferred) or diodes, you are doing it wrong, and asking for trouble.

Here's one right way.

Dec 16, 2016 | 01:38 PM

#28

donny_wong

Newbie

Joined: May 2016

Posts: 6

Likes: 0

Quote:

Originally Posted by BlueRidgeMark

If you are not isolating the existing circuit with either a relay (preferred) or diodes, you are doing it wrong, and asking for trouble.

Here's one right way.

tsd fix didn't really work for me. i really think my xj doesn't like winter fuel. i did do the delay fan mod , if i get a couple requests i can make a video showing function , i used a turbo timer instead of the other delay timers that are on this forum.. use relay and diode also. pm me so i can get motivated to make a youtube video. it cost me 20 dollars to make and has a digital display and is easy to set the time.. let me know guys. check out my channel on youtube if you get a chance. https://www.youtube.com/channel/UCSv...view_as=public

Dec 16, 2016 | 08:28 PM

#29

IJM

CF Veteran

Joined: Jan 2014

Posts: 1,539

Likes: 351

From: District of Columbia

Year: 1998

Model: Cherokee (XJ)

Engine: 4.0

Quote:

Originally Posted by BlueRidgeMark

If you are not isolating the existing circuit with either a relay (preferred) or diodes, you are doing it wrong, and asking for trouble.

Here's one right way.

I did it exactly the way you recommended in your writeup, and it's worked perfectly every since. By the way, a 30-amp fuse is what you need for the fan circuit. I tried a 15 amp, and that blew right away, the 20 amp I replaced it blew after a couple of days, and the 30 amp has been fine every since.