OK, this topic started as an offshoot about a question of towing and what aditional things would need to be done to a KJ to prepare it for hauling a heavy load. Please debate only the differences between Mechanically driven fans and Electrical Fans.

My argument: A mechanical fan is better for towing because the fan blades can be more aggressive and will move more air past the radiatior surface to aid in cooling during low speed, heavy traffic situations. Where as a electric fan can not have as aggressive fan blades because they are limited by the amount of current draw, motor size and packaging space available on any vehicle.

In practice (as far as I know) all vehicles were equiped with a mechanically driven fan up until the invention of FWD cars. At that time, the waterpump was not directly behind the radiator and as such the electrical fan was implemented.

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02 Liberty Limited
Silver Outside & Taupe Inside
Heated Seats, Sunroof & Infinity speakers
USA Spec I-Pod adaptor, Mopar Sub, Garmin GPS
Tow Package, Select-Trac
Rock Rails, Tow Hooks

Jason, an electric fan still puts a load on the engine because the alternator needs to replenish the power consumed by the electric fan. If an electric fan only uses 240W of power, then I don't see why a mechanical fan would use much more. Power is power, whether electrical or mechanical. Although the mechanical fan does have the less efficient viscous clutch, converting from mechanical to electrical to mechanical power for the electric fan can't be that efficient either. Please explain further.

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Jeep Liberty Wikibook
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as I stated the alternator at full load is no different then at no load as far as resistance to the engine so fuel is saved

A good read to help out BOTH sides
long but I feel it is needed to under stand how things work befor we go on

The Mechanical Radiator Fan and Fan Clutch
   The standard engine cooling (radiator fan) on many vehicles is of the mechanical type, meaning that it is belt-driven. In most cases the mechanical fan is mounted to the water pump snout and is driven off of the same pulley that rotates the water pump. The mechanical fan is very simple, and effective for most applications. The mechanical fans are typically made of stamped steel, but some aftermarket fans can be fiberglass, or riveted stainless blades to a stamped steel center section. Blade count varies by application, some have 4, 5, 6 or 7 blades.
   Benefits of this type of fan is that it is cheap, it's simple, and it is always running. But, these can also be adverse affects. A fan that runs all the time takes power to make it work. Plus, this type of fan is not optimized at all engine speeds. Where some fans may work great a cruising speeds, they may be horrible at idle speeds (like stop and go traffic), or at higher engine speeds. Using an aftermarket fan increases airflow for better cooling, but at the expense of noise and at times even power. Some fans, like the riveted fans, can explode at certain upper RPMs and damage other engine and vehicle components.
   A better street performance and at many times street/strip fan is using a mechanical fan with a fan clutch. The fan clutch is designed to drive the engine fan when air movement is needed to cool the engine. A thermostatically controlled fan clutch employs a bi-metal spring to adjust fan speed in response to operating temperature. As engine temperature rises and the radiator heats up, the air passing the radiator into the fan heats the spring coil and a silicone fluid in the clutch that enters the chamber increasing tension in the clutch and drives the fan. As coolant temperatures reduce, the fan clutch is allowed to slip, offering increased fuel efficiency and quieter operation. On the "non-thermal" fan clutch a silicone fluid with a very high shearing capability is used to drive the fan and cool the engine at lower engine speeds. As RPM increases the drive fluid allows the fan clutch to slip, increasing engine efficiency when less fan-assisted air movement is needed due to higher vehicle speeds.
   Because the fan clutch and water pump share a common shaft, if the fan clutch fails it usually takes out the water pump bearing with it. To tell if a fan clutch is failing, use these common symptoms.
• The fan clutch locks up, thereby spinning at the same RPM as the water pump. This is obvious by increased fan noise and reduced fuel efficiency. You can test this by grabbing the fan with the engine OFF and trying to turn the fan. If there is excessive resistance, or you cannot spin the fan, the fan clutch should be replaced.
• The fan clutch will not engage and fails to turn the fan. The fan may still spin, but only as a result of centrifugal force from the already spinning pump. If you try to spin the fan with the engine OFF, the fan will spin freely with virtually no resistance. Replace the fan clutch.
• The fan clutch explodes. This is usually caused by severe bearing failure. Fan and fan clutch parts will contact and damage the hood and other under hood engine components (belts, hoses, battery, wiring, radiator, etc.) NOTE: This is almost always due to vehicle owner "laziness" in that one of the two items above had already occurred and were ignored or not periodically inspected.
   Generally, fan clutch output under normal operating conditions will decrease by about 200 RPM per year. So, a three year old fan clutch is possibly due for replacement, or at least more periodic inspections. A four year old fan could very well be running partially disengaged and should be replaced.

The Electric Fan
   Many new cars are taking advantage of electrical cooling fans because of their smaller engine compartments and greater airflow demands. It is well known that an engine can cool itself at cruising speeds of roughly 60 miles per hour in an average climate. But, with tighter under hood tolerances, unleaded fuels, higher combustion temperatures, forward mounted catalytic converters, and other issues, a mechanical fan is not only not practical, but inefficient.
   In the past, electrical cooling fans were "helper" fans for heavy towing and performance applications. But now, many enthusiasts are dumping their mechanical fans in favor of the more efficient electric counterparts. Noise is reduced, horsepower is gained, mechanical water pumps last longer, and more efficient low speed cooling are all benefits of the electric fan.
   If you are exchanging a mechanical fan for an electric, be aware that proper shrouding and airflow requirements are still a concern. You cannot just mount an electric fan and think it will solve all your problems. Correct mounting location, fan shroud installation, the correct fan (or fans) to meet the airflow demand (calculated by engine horsepower, vehicle weight, altitude and load) are all important if you want to do it right. Many aftermarket fans are rated by horsepower, and do not be surprised if in many cases you cannot find the fan that meets your power requirements. The only trick I can offer is to cover as much surface area of the radiator as possible, which may very likely mean multiple fans, and use a "puller" fan if it is your primary fan and a "pusher" if using it only as an auxiliary. Never use both a pusher and puller electric fan on the same radiator.

Another plus for electric fans is they still will pull the same CFM even when your crawling at 5 mph on the trail to better help keeping the engine cool.If you add a aftermarket fan you can also wire it in to turn on/off with a toggle switch which I did on my '84 blazer I used for mud racing.I could keep the fans on with the engine on helping the engine cool down faster between runs(when hot the coolant will still "flow" due to thermal convection).

If there were no change in resistance to the engine than we'd be creating energy out of no where. Is an engine -> alternator -> fan path more efficient than an engine -> viscous clutch -> fan path? Since the efficiency of a typical automobile alternator is 90%, it very well could be Still doesn't asnwer the question, why does the mechanical fan come standard without the tow package on the Renegade?

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Jeep Liberty Wikibook
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as was stated in the artical I posted
less parts to break and not affected by mud and water the DOWN side to electric or so some would think
but just as tjkj2002 stated they can be wired to a swich and turned off
so they put the mech fan on the Renny. cause they know that people wach to much TV and will go out and plow into mud and water at 30mph and tink it "cool"

I am saying that an alternator at full load is very easy to turn VS the fan at lock up just look at the size of the pully on the alternator VS the one on the water pump that should be a dead give away

Look folks dont get me wrong if you are happy with the mech. fan then go for it but I have seen way to many newer stock jeeps runnig hot/warm out on the trail to belive that the mech. is better when guys running heavy mods with big V-8's and electric fans with no problems at all

I know that my TJ with the mech fan gets warmer than I like when trail riding but the KJ stays right on normal all day in the heat with the AC on

That is a good read. A few things I've noticed from my own experience

1) If a thermatically controlled cluth fan fails - fluid leaks from the clutch but the fan doesn't take out the water pump.
2) There is an increased load on the bearing surface from the weight of a fan
3) The fan will move with the engine since it's attached to it. Therefore you need a bigger clearance around the shroud which means less efficency

For an electric fan
1) The Linclon MarkVIII fan sounds like a jet liner taking off when it's not hooked up to a controller and running at 100%
2) They don't allow for DEEP water crossings
3) Mud can cause the fan to stop working on a trail
4) If the fan turns off.... well - look for a highway


While I agree that an electrical fan is supperior for most daily driving, off roading condidtions. I believe that a mechanical fan is vastly superior to an electrical fan for towing applications where the engine RPM will be higher (no overdrive)

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02 Liberty Limited
Silver Outside & Taupe Inside
Heated Seats, Sunroof & Infinity speakers
USA Spec I-Pod adaptor, Mopar Sub, Garmin GPS
Tow Package, Select-Trac
Rock Rails, Tow Hooks

yes but at highway speed the fan does nothing so how would it help?

you need to be doing about 65+ for the air flow to overtake the fan.

What about on 55MPH country 2-lane roads / highways?

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02 Liberty Limited
Silver Outside & Taupe Inside
Heated Seats, Sunroof & Infinity speakers
USA Spec I-Pod adaptor, Mopar Sub, Garmin GPS
Tow Package, Select-Trac
Rock Rails, Tow Hooks

so a mech. fan with the engine trning at 2000-2500 rpm will push the air at over 60mph?
I think not cause if that were so you could feel the wind coming from the rear of the jeep like crazy it may blow at best 30
think about it at 5mph in 4low turning about 1500rpm the leaves barely move under a jeep with a mech fan and then you need to be turning 1500 rpm as with an electric fan the jeep can turn 600rpm and move more air or 2000 rpm and move the same

Read where on most transverse engine cars (electric fan), the fan is about useless over 40 mph with a normal load in moderate climates. If you have enough load or it's hot enough to get the H2O temp up it might kick in at highway speeds.

The CRD has both fans. The only time I hear the electric fan running is while stopped in traffic with the A/C on.

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2005 Liberty Sport CRD, Lt Khaki, sunroof

Thankful to now be an EX-CRD owner.

As far as the extra load on the alternator with a electric fan is not that bad.Vehicles that come with a electric fan from the factory(like the KJ) have a higher output alternator.Say your alt is rated at 100 amps,at idle it's putting out about 60 amps,at cruising speeds it's putting out the full 100 amps(all made up numbers).When offroading in 4-low your engine is turning about the same as it would at cruising speed to the alt is putting out full power.Your ignition doesn't draw that much amps and all other electical items added together leaves plenty of amps left(unless you have a big stereo).My point in all of this is 30 years ago is most alt put out 55 amps max and today most put out over 100 amps and are more effeciant than the older ones,thus robbing less power from the engine.Anyway you go you have good points and bad points,figure which has more good for what you are going to use it for and go that way.

In my opinion...I know ...who asked for your opinion....However you can keep the engine temp at around 200 degrees is the best method either way you go. But on a more serious note I'd be more worried about trans. temp. under wheeling conditions.

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Ron
03 Red Libberty Sport
3.7 V6 Auto 4x4
Lifted
Cooper Discover ATRs 265/75/16
American Racing 16x8 Polished Baja Wheels
Moog Lower Ball Joints
Member#051397 L.O.S.T. Midwest

The tow package liberty comes with a extra cooler from the transmission (or at least mine did.)

I would like to know why there is a mechanical fan that is also included with the tow package if it is not really necessary

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02 Liberty Limited
Silver Outside & Taupe Inside
Heated Seats, Sunroof & Infinity speakers
USA Spec I-Pod adaptor, Mopar Sub, Garmin GPS
Tow Package, Select-Trac
Rock Rails, Tow Hooks

Alternators don't supply current unless it's needed. There needs to be a load for there to be a current draw. The alternator may be capable of supplying 100A, but if you're not running any accessories, then you're not actually taking that much power from the engine. The power required to turn the alternator is proportional to the load on the alternator. With an electric fan, you're adding a load to the alternator which is then transferred to the engine. Assuming identical air density, fin shape/size, and fan speed/efficiency, the same power is required to drive both a mechanical and electrical fan. Energy can't be created or destroyed; increased efficiency is the only way to achieve the same output with less input. 10% power is lost converting mechanical energy to electrical in the alternator then another x percent is lost converting electrical to mechanical in the fan. y percent is lost in the mechanical fan viscous clutch. If 10% + x > y, then the electrical fan is less efficient. I welcome constructive criticism, please feel free to tear my statements apart.

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Jeep Liberty Wikibook
# cd /home/fuzzymuzzle.com

Most likely to keep from cooking the transmission.

Just wondering if your transmission cooler is combined with the A/C condensor as a single unit? Electric fan sit directly in front of this assembly. This is the first vehicle I've seen plumbed like this, seem like an odd combination. Then again what should I expect, it's a CRD.

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2005 Liberty Sport CRD, Lt Khaki, sunroof

Thankful to now be an EX-CRD owner.

A mechanical fan pulls hot air from the radiator(with the hot tranny fluid in it)while your towing and heating up the tranny.An electrical fan pushes cool air across the a/c condensor to cool the freeon while it's in a liquid state at appr.250 to 300 degrees. That's why the electric fan cycles in sync. with the a/c compressor.....Make sence?

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Ron
03 Red Libberty Sport
3.7 V6 Auto 4x4
Lifted
Cooper Discover ATRs 265/75/16
American Racing 16x8 Polished Baja Wheels
Moog Lower Ball Joints
Member#051397 L.O.S.T. Midwest

RFCRD, from what I've read, Jeep Libertys with the 42RLE transmission have an auxiliary transmission cooler bolted in front of the engine radiator. Libertys with the 45RFE transmission have a cooler built into the engine radiator. Liberty CRDs with the 545RFE have a combination transmission cooler and A/C condenser bolted in front of the engine radiator. It seems your observation is correct.

LiLredLibby, on my 05 Renegade, both the electrical and the mechanical fan are on the engine side of the radiator. Both are pulling relative to the radiators.

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