Need Help putting a switch on electric fan
Thread Starter
CF Veteran
Joined: Jun 2011
Posts: 1,492
Likes: 0
From: KY
Year: 2000
Model: Cherokee
Engine: 4.0 L6
Ok so i want to put a switch on the stock electric fan and was wondering if anybody can tell me the best way to do this...post pics if u have any...Thanks
Junior Member

Joined: Feb 2012
Posts: 74
Likes: 5
From: Northwestern PA
Year: 1998
Model: Cherokee (XJ)
Engine: 4.7
Do you mean a fan override switch? If you do, I am testing one now. My system overrides the factory fan relay through the ground signal from the computer. This way I can keep the fan on when the temperature falls below the factory set point. So I am going to test this a while before I can get pictures and wiring diagrams to you just to be sure it works. I am new to Cherokee forum and I don't get a chance to check it everyday so please be patience with me. I enjoy Cherokee forum. I hope I can help you guys with my 25+ years as a mechanic and 30 years off road experience.
CF Veteran
Joined: Jan 2011
Posts: 1,635
Likes: 0
From: Virginia
Year: 1999
Model: Cherokee
Engine: 4.0
I have it done to my 99, All I did was run a switch off the dash, Power the switch from an auxiliary power at the fuse panel and then run a wire from the switch and TAP into the green wire on the electric fan that way with the switch in the off position the fan still works when the temp gets to high and the computer tells it to come on, Or I can just flip the switch when ever I want and manually turn it on.


Last edited by aquickmopar; Apr 29, 2012 at 02:15 PM.
CF Veteran
Joined: Nov 2011
Posts: 2,433
Likes: 6
From: Northern MN
Year: 1990
Model: Cherokee (XJ)
Engine: Renix 4.0
I took the easy way out and ran 12 gauge wire from the battery to a switch inside and then to the power wire on the fan. 30a fuse at the battery and a 30a rocker fuse from radio shack. I only use it in town and when I'm towing so it works for me. The wiring and switch get warm though.
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CF Veteran
Joined: Apr 2011
Posts: 14,553
Likes: 1
From: Carrollton, GA
Year: 1994
Model: Cherokee
Engine: Inline 6 4.0L High Output
CF Veteran
Joined: Apr 2011
Posts: 14,553
Likes: 1
From: Carrollton, GA
Year: 1994
Model: Cherokee
Engine: Inline 6 4.0L High Output
CF Veteran
Joined: Apr 2011
Posts: 14,553
Likes: 1
From: Carrollton, GA
Year: 1994
Model: Cherokee
Engine: Inline 6 4.0L High Output
I've never heard of that... Not to discredit it just saying. Besides with a diode the current can only flow one way so i don't imagine that being possible, with a diode correctly placed in the circuit
Seasoned Member
Joined: Mar 2010
Posts: 379
Likes: 1
From: Modesto
Year: 1993
Model: Cherokee
Engine: 4.0 high output straight 6
I have it done to my 99, All I did was run a switch off the dash, Power the switch from an auxiliary power at the fuse panel and then run a wire from the switch and TAP into the green wire on the electric fan that way with the switch in the off position the fan still works when the temp gets to high and the computer tells it to come on, Or I can just flip the switch when ever I want and manually turn it on.




CF Veteran
Joined: Apr 2011
Posts: 14,553
Likes: 1
From: Carrollton, GA
Year: 1994
Model: Cherokee
Engine: Inline 6 4.0L High Output
Now correct me if I'm wrong but if your running power from your own switch to the green wire, and if the fan relay WOULD kick on for any reason what so ever with it's own power source from the relay, wouldn't that create a positive to positive and fry your wiring pretty much instantly?


