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Discussion Starter #1
Ive got an 01 G.C. w/4.0 eng. And my radiator fan and module have died a death. Im looking for any input/info/suggestions that anyone has on these things. Id like to "improve" on the stock setup but dont want to go too far down the aftermarket road. Ive done the usual search on line but not sure if the ones ive found are worth a s#$! A $15 module and a $40 fan sound good but dont make me feel good. Lol
Anyone have any input?
Thankyou in advance
 

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You have a ZJ Platform JGC, this section of the forum is for WK2 Platform JGC's that is two Generations later than yours. You'll likely get better responses if you post in the right section with posters more familiar with your vehicle.....

I don't know, but for almost all vehicles in the '01 era, there is no fan module, its controlled by PCM (or ECM) when you say module are talking about the Relay? Some vehicles even back then were also using PWM to control the fans, and require a darlington pair of mofset transistors to pass along the square wave signal at high current, they called it a solid state relay, but in reality its just a heavy duty resistor pack.
 

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Discussion Starter #3
Mongo53, lol. Oops! I thought i had posted in a "general, JGC" group, however, your info is helpful. The service manual says "...fan speed control module" i was assuming that it controlled the fan by pulse width or something along those lines. Anyway, ill remove and repost in the correct group and thankyou for sharing your knowledge. I do appreciate it.
Keep the shiny side up!
T2tj
 

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Mongo53, lol. Oops! I thought i had posted in a "general, JGC" group, however, your info is helpful. The service manual says "...fan speed control module" i was assuming that it controlled the fan by pulse width or something along those lines. Anyway, ill remove and repost in the correct group and thankyou for sharing your knowledge. I do appreciate it.
Keep the shiny side up!
T2tj
The Forum is broken up by Platforms, which makes the most sense, since when a particular model switches to another generation, its a new platform, thus different platforms have different equipment, common problems and fixes.....

Pulse Width is PWM, I don't know for a fact on the ZJ, but just about all modern cars, the engine computer controls the fan, but the engine computer can't possible handle the current necessary to power the engine fan. So the engine computer has some sort of component to handle current that it triggers....
  • Simple fans that turn on and off, its just a relay....
  • There two speed fans, so the PCM might trigger multiple relays for multi-speed motors....
  • With the two speed fans, they might even put a thermister in the fan, so the fan controls it speed based on the heat, then if its getting too hot, the PCM will trigger the higher speed for the fan to cool it down....
  • Then there is PWM, where the engine computer will generate a square wave (a.k.a. a series of pulses, which the width of those pulses as you look at the signal plotted out, will dictate the power or speed of the device being controlled, that's where pulse width comes from).... a relay can't open/close fast enough to be used for these Square Wave, they instead use a high power amplifier that changes the square wave of milliamps to the same square wave of 10's of amps.....
So this amplifier for the square wave from the engine computer is likely what they are calling the "fan speed control module".... ...in my Neon R/T, they called it a "Solid State Relay".... ...but it was just several mega heavy duty hi-power transistors that acted as an amplifier for the square wave from the engine computer....
 

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Wow big difference between GC's and XJ's of that era.
My 2K XJ's efan is a bare bones system, its either on full speed or off via a simple relay controlled by the PCM.

What do you mean by improving the stock set up?
Is the fan system malfunctioning or is the engine overheating?

I believe Mongo is correct since you apparently have a PWM modulated fan speed control system.
I looked up your year's fan module at Rock Auto and its as Mongo said looks to be just a transistor based power amplifier at around $25.

Far as i can tell not much you can improve the fan speed with that kind of a system at least easily.
The only way i can see is to bypass the stock system and install an after market fan motor controller complete with temperature sensor to automatically turn the fan either full on or off depenendent on the radiator temperature.

Or if you have over heating issues like i do with my 4.0, i wired up an aux switch that turns the fan on or off unconditionally with an additional relay. I also incorporated a timer off circuit to take care of the heat soak problem in hot weather.
 

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Discussion Starter #7
I was thinking "improve..." by using a higher cfm fan or better motor etc. Possibly even doing away with the electric fan and going with a fan clutch/fan set up.
Ive never had any problems with the system as is until the controller and fan motor recently went belly up. Im in San Antonio Tx. so "winter weather" is very rare.
Lol. We close our roads at the threat of a frost. Lol
 

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In that case, i'd replace the fan 'n motor combo and the controller and see what happens.
See'n its a an '01 they both might be due for a replacement anyhow.

There are higher after market CFM fans available out there out there which have primarily different and more efficient fan blade designs.
If you go a higher CFM after market fan, i'd make sure its plug 'n play for your Jeep.
Or else there might be connector or fitment issues.....but that wouldn't stop me as i can jury rig just about anything to work.

By the way up here in the Frozen Winter North tundra Midwest, the main highways only close if there's at least 4 feet of snow. And thats usually only temporary til the snow plows try to do their work.
The side country roads out here are a different matter.
Been snow or ice bound for a couple days a few times out here.
Cabin fever? Yep!
 

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Discussion Starter #9
Thanks for your input.
I dont believe Texas has had 4 foot of snow yet! Even if you were to add all of those brief instances together. Lol
Drivers down here have enough trouble driving in the rain let alone snow and ice.
A few years ago an afternoon shower "caused" 300+ accidents in just a few hours.
Shameful it is.
 
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