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Unread 03-19-2003, 07:54 AM   #1
pHaZe5unIt1
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Thinking of switching to an elec. fan

I was thinking about switching to a electric fan rather than the stock belt driven one has anyone done this. If so any pointers.
I was thinking of doing this to save gas miles, think of it you are spinning this huge fan and its wasting the accel. and gas:shrug:
also do they make underdrive pullys for these cars.

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Unread 03-19-2003, 11:14 PM   #2
Stocker
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Interesting idea and I hope you hear from someone who has done this. As you are probably aware, the clutch fan *at least in theory* engages as required for engine cooling, and much of the time when the vehicle is in motion, air flow alone provides cooling, and the clutch allows the fan to free-wheel, so as to not rob power and fuel.

Similarly, there is no free lunch, and electric fans also need power to operate, and the additional electrical drag does affect mileage and power somewhat. That said, it *probably* robs less power and fuel than the clutch fan. And operated by a thermostat, it too would run only when needed.

Okay, I got a bit wordy, sorry. Let's hear from somebody who has done this! Any measurable gains? These 5.2Ls are thirsty and we could use some relief!
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Unread 03-20-2003, 02:06 PM   #3
Intrepidjeep
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Well, the fan never truly freewheels. I believe the clutch is a viscous clutch that allows more slippage when the engine temperature is cooler, and less slippage as the temp climbs.

It's pretty easy to see why this is true -- at any time the vehicle operator may engage the AC compressor (either as part of defrost function or for cooling the passenger compartment).

Mere seconds of no airflow across the AC condensor can cause such a pressure spike in the system that it damages the compressor, blows a hose or causes coolant to vent to the atmosphere.

Then you realize that all cars either have an electrically activated fan (for instant airflow any time the compressor is engaged) *or* a clutch fan that never totally freewheels.

Electric fans are also nice for deep-water fording -- you're less likely to have radiator damage from an electric fan, as the blades hit the water and bend toward the radiator fins.

I've not electric fan(s) this on the Grand Cherokee but I have done it on other vehicles. It's not at all hard to generate enough airflow for cooling -- it's a little harder to generate enough airflow for the AC condensor! Especially on a hot day, the condensor really needs some good strong airflow. The easy setup (if you have room) is a small-to-moderate-size 'puller' fan behind the radiator, and a similar size 'pusher' fan in front pushing air into the condensor. In our Grand Cherokees, there's not much room up front for anything in front of the condensor, so you probably have to stick with a single-fan solution.

It would be nice to hear what's the best fan to use (big enough to provide the power, small enough to still fit behind the radiator, and preferably reasonably quiet). The mechanical fans can use a surprising amount of power, and the electrical ones as well, but the electric fans can truly freewheel -- be turned off -- and would stay freewheeling as long as your airspeed remained enough to cool the engine (around 25mph) or higher.

Of course you want it thermostatically operated, but a kill switch would be great for deep-water conditions. Might be worthwhile to run two smaller fans rather than a single large one, depending on how it all fits in there . . .
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Last edited by Intrepidjeep; 03-20-2003 at 02:10 PM..
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Unread 03-20-2003, 04:33 PM   #4
Stocker
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Intrepidjeep - True, true! Thanks for catching me; yes, the fluid allows more slippage, the fan doesn't actually free-wheel. And you pointed out several other things I missed. Great post!
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Unread 03-20-2003, 05:51 PM   #5
ZR7 Ken
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The '98 5.9Limited ZJ used an electric cooling fan. Perhaps you could at least use the fan assembly itself, and maybe the sensor/ upper radiator hose.
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Unread 03-20-2003, 05:56 PM   #6
Intrepidjeep
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Oh, now wouldn't that be ideal!! A factory fan, you know it'll be more than enough airflow for any engine that goes in the Jeep. Have to get the rest of the parts, thermostat, etc.

On the other hand, the fan might be computer-controlled, but you could just get the fan and rig up your own separate thermostat, relay and power.
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