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Aux. Electric Fan Override?

Kevin

NAXJA Forum User
Location
Richmond, VA
Has anyone tried to do this? If I understand correctly, the electric fan comes on when the engine temp exceeds a certain point. I was wondering if it is possible to bypass the relay that does this and just put a toggle switch in parrallel to the relay. That way, if I wanted the fan on when crawling, I could stay ahead of my overheating temps, and if I had the switch off, the relay could still do its thing. Will this work?
 
Well, i haven't looked to extensively into the jeeps, but on the neons they have a fan relay control circuit (solid state) and the pcm grounds the relay for the fans to turn on. Depending on how much time they are grounded depends on how many volts the fans get. If the pcm grounds the fans for say 30% of the time, they only get a small voltage (say 4 volts) so they run very slowly, and when the pcm grounds the fan relay 100% of the time, the fan runs 100% of speed.

Did I answer your question? It should work, but you have to figure out the fan control relay or run a normal relay the would trigger the fans to run.
 
if you do a search on this you will find lots i just saw a post about it a few weeks ago and they do sell a plug in kit all set to go that does just what you said:)
 
go to www.xj-armor.com and take a look at their kit. They have some photos which should help you in making one or just buy theirs, the price is pretty cheap and it comes complete with everything pre-wired up with a switch. I have it on mine and it was a simple plug and play kind of thing. Juice
 
You can by one from xjarmor on ebay for 36.00 comes with oem style plugs, relay, and switch.
 
Go to Radio Shack, & pick out a switch you like, some hook up wire, & a fuse adapter. Then just bypass everything & wire it straight to the fuse box. Then you decide when the fan comes on. Probably cost you $10-$15

Rob
 
When I did the closed cooling system upgrade to an open system, I lost the bung for the fan switch. I cut the wire off the factory automatic switch, ran wires to a switch on the dash and now control the fan from the dash at my convenience. It still comes on automatically when using the A/C. 3 years and 100k miles later and it still works fine.
 
I have my aux fan on a toggle on my '96. It will come on three ways (a) via toggle, (b) via AC on, or (c) when engine temps reach 208*. Tap into white wire with a splice connector, so you don't have to cut any existing wires. Run it to a relay under the hood. Power the relay to (+) battery, ground relay to something metal, and run relay to toggle inside jeep. A toggle, relay, wires, and connectors will cost you about $15 at Pep Boys. If you're not sure how to hook up the relay, get a kit - it'll have instructions. It'll be a sweet setup and will allow the fan to come on with the toggle off via the ECU, in case you're too preoccupied wheelin' to flip the switch. LOL.
 
"The kit from XJ armor only works for post '97 XJs. The connectors wont hook up to 97 and later style."

Huh? I think you've got a typo there somewhere. Does it work for '97 and later, or for PRE '97 models?
 
I cut the wires on the fan, put in an in-line fuse and ran a switch to my dash, cost me $11 Canadian and works great! Bought the switch, fuse holder, and 14 gauge wire at Car Quest!
 
I meant the kit only works for PRE 97 XJs. Yes its true you can vut the wires and modify it but their website says fits all XJs 1984-2001. I just wanted everyone to know that in the form you recieve it it will not just hook right up to post 97 XJs.

A side note: For non-Renix XJs, (ones without the temp sensor mounted in the radiator tank), the PCM controls the aux. fan and you must run a relay and a switch to avoid sending 12 volts back to the PCM.
 
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