Just wondeing what the purpose of the front mounted (between the grill and intercooler) electric fan is? Does this fan come on when the AC is on, or does it have some other temperature based function?

Just wait till summer time while idleing or in traffic you will hear it kick on ...........so yes it is temperature based function.

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'05 Bright Silver Sport CRD
245/70/16 BFG AT KOs (On the second set now.....First set was replaced at 106K miles)
some stereo stuff.........
L.O.S.T. #053490

I heard mine running today, just so happen to let it idle when I was dropping something off to a friend.

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2006 Black Jeep Liberty CRD Limited
K&N, Samco Hoses, Michelin 245/70-16 LTX A/T2, Fumoto F-102, V-Force Muffler, Mopar, Hitch, Trailer Wiring, Skid Plates, Slush Mats, Rear Shelf, Predator Stage 1, Transgo, ORM & CodeReader, Facet 40109 Pump
"IT'S A DIESEL THING, YOU WOULDN'T UNDERSTAND"
Certified Services Auto & Truck Repair

Cool, I was thinking it was AC based. I did my electronic heater control AC bypass, and I was try to test to make sure the AC was coming on, I didnt see the fan come one so I thought maybe my wiring wasnt working. It was so cold out i couldn't tell by putting my hands in front of the vent and testing air temps.

So my electronic bypass is probably working then, yay!