derf

The SJ (Grand Wagoneer) created the luxury SUV market. The ZJ took its place when they phased out the SJ.

As far as dual fans, the shape of the radiator mandated it. It's wide and short. No good way to have just one fan on it.

Mechanical fans move a ton more air but are a bigger parasitic loss, reducing fuel efficiency. The engineers figured out that having the primary fan as mechanical gave the engine the cooling it needed for normal driving down the road. The electric fan gives the cooling system enough of a boost when you're sitting idling or working the engine hard. So they have a smaller mechanical fan with less parasitic loss than one big one. And they have an auxiliary helper fan when the smaller mechanical fan isn't quite enough.

It's actually a pretty smart way to balance the cooling needs with fuel efficiency desires.

PatHenry

European auto companies must love the uni-frame design. Fiat was seriously considering going to uni-frame on the Wrangler, among other weight reducing/mpg increasing ideas...

Tbone289

^ This. IMO, it's a packaging consideration. There's no way to cover enough surface area with a single fan on a radiator of this shape.


I agree.

derf

Even before AMC became AMC, the companies that would form AMC were doing uni-frame designs. Once AMC bought Kaiser, it was only a matter of time before the uni-frame Jeeps started to come out.

But within the Wrangler division, there is tremendous resistance against going away from traditional body on frame. It may eventually happen but they aren't going down without a fight.

PatHenry

Thank God for that!

Yeah, I remember a lot of considerations that were just unsettling - going away from solid axles, uni-frame Wranglers, ditching the stick shift.

I'm glad to see they haven't given in on any of the above (though my dreams of a diesel stick shift wrangler are far from reality.. )

I've often wondered why FCM hasn't considered a new XJ type Jeep (uni-frame with Wrangler engine/tranny and quality/durability)... I'd do it as an XJ2 model (since those new KL's currently shame the name "Cherokee")

kbeam418

Money and at the time electric fans were not as efficient. Mechanical fans can move A LOT of air with not a whole lot of power loss even today a mechanical fan will move more air than an electric fan hence the reason why 3/4 ton trucks still use them. Chrysler only put the electric fan in for vehicles equipped with A/C, condensers put off more heat than radiators so the engineers will typically have an electric fan to keep the A/C working good. I myself prefer mechanical fans because you only have part that can fail (clutch) and it takes 15 minutes and $40 to put a new one in. Electric fans have a cts, wiring, relays and the brushed motor itself that can fail.

Waynerd

E fan relays are a pretty common failure on the WJ. Messed up part is that they put them in a nearly inaccessible location. Lol.

iroquoisrenovations7@gmai

my son has a 2007 jeep Cherokee and has no clutch fan on it and I thought that was dum...I dont get it.....but has no overheating problems which got me smh....but maybe I'm just old school

4.3L XJ

That is correct. It is the shape of the radiator that dictates two fans. The mechanical pulls 2/3 of the air and electric the rest. It could have been done with two electric, but two mechanical would have been a challenge due to the engine moving under torque

iroquoisrenovations7@gmai

Do I need the electric fan if I got a mechanical one?

4.3L XJ

Yes, you do. You need it to draw anough air across your AC condenser coil or if the engine begins to overheat