Many newer pickups use an electrically engaged fan clutch. Dodge and ford since 03.on the 5.9/6.7 Cummins and the 6.ohno.
Does a clutch fan take power or no?
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As stated above, the viscous clutch designs are more reliable than an electric.
Our aftermarket upfitter replaces all our service vans factory thermostatic fan clutches with centrifugally clutched units due to extensive stationary operation. I have asked them many times why they don't upfit electrical fans and they repeat that electric units are not as reliable...
Our aftermarket upfitter replaces all our service vans factory thermostatic fan clutches with centrifugally clutched units due to extensive stationary operation. I have asked them many times why they don't upfit electrical fans and they repeat that electric units are not as reliable...
Wow, lots of misunderstanding about a piece of 1960s tech on this thread...
1) The clutch fan doesn't "stress" the alternator. It does put a load on the belt, but then the alternator would do exactly the same if it were generating the extra electricity to run an electric fan.
2) Fan clutches do wear out and/or leak fluid. But they're usually good for on the order of 100k miles or more, depending on a lot of conditions. They're not a friction clutch, they're a fluid clutch so there's nothing actually wearing down in them.
3) Viscous clutches never TOTALLY decouple the fan unless the fan is physically blocked, then they go into a self-preservation mode. They do reduce the coupling factor WAY way down so that the fan may just barely be turning at idle on a cold day, but they never 100% de-couple. They never turn to a 100% solid coupling, either, they always slip at least a little bit.
4) There ARE fan clutches that do completely de-couple, but they're electrically operated like an AC compressor clutch. They're commonly found on bigger diesel trucks and offroad equipment, although Horton used to make them for things like Ram pickups with the Cummins diesel (maybe still do). They go from dead quiet to "God's own vacuum cleaner" noise levels when they engage- you can hear big truck fans kick in if you pay attention. Did some googling, and apparently Dodge actually offered a hybrid viscous/electric fan clutch as OEM on the Cummins.
5) Viscous clutches always couple fairly hard on start-up, even when stone cold, hearing the fan roar loudly on a cold start doesn't mean the fan clutch is bad. After running for 10-20 seconds, they'll decouple if the engine is cold.
1) The clutch fan doesn't "stress" the alternator. It does put a load on the belt, but then the alternator would do exactly the same if it were generating the extra electricity to run an electric fan.
2) Fan clutches do wear out and/or leak fluid. But they're usually good for on the order of 100k miles or more, depending on a lot of conditions. They're not a friction clutch, they're a fluid clutch so there's nothing actually wearing down in them.
3) Viscous clutches never TOTALLY decouple the fan unless the fan is physically blocked, then they go into a self-preservation mode. They do reduce the coupling factor WAY way down so that the fan may just barely be turning at idle on a cold day, but they never 100% de-couple. They never turn to a 100% solid coupling, either, they always slip at least a little bit.
4) There ARE fan clutches that do completely de-couple, but they're electrically operated like an AC compressor clutch. They're commonly found on bigger diesel trucks and offroad equipment, although Horton used to make them for things like Ram pickups with the Cummins diesel (maybe still do). They go from dead quiet to "God's own vacuum cleaner" noise levels when they engage- you can hear big truck fans kick in if you pay attention. Did some googling, and apparently Dodge actually offered a hybrid viscous/electric fan clutch as OEM on the Cummins.
5) Viscous clutches always couple fairly hard on start-up, even when stone cold, hearing the fan roar loudly on a cold start doesn't mean the fan clutch is bad. After running for 10-20 seconds, they'll decouple if the engine is cold.
Originally Posted By: SteveSRT8
As stated above, the viscous clutch designs are more reliable than an electric.
Our aftermarket upfitter replaces all our service vans factory thermostatic fan clutches with centrifugally clutched units due to extensive stationary operation. I have asked them many times why they don't upfit electrical fans and they repeat that electric units are not as reliable...
I've always wondered that. Seems like electric fans would cool better. Mechanical fans will move a MASSIVE amount of air ... but the engine has to be spinning fast for it. The electric fans can move 100% of air with the engine idling.
From the factory, a lot of Cherokees with the 4.0L engine came with an electric and mechanical fan. The mechanical fan, when working properly, should keep the coolant temp at 210-220 under normal operating conditions. Mine does move a lot of air, even at idle. And when I rev up the engine, it sounds like a semi!
As stated above, the viscous clutch designs are more reliable than an electric.
Our aftermarket upfitter replaces all our service vans factory thermostatic fan clutches with centrifugally clutched units due to extensive stationary operation. I have asked them many times why they don't upfit electrical fans and they repeat that electric units are not as reliable...
I've always wondered that. Seems like electric fans would cool better. Mechanical fans will move a MASSIVE amount of air ... but the engine has to be spinning fast for it. The electric fans can move 100% of air with the engine idling.
From the factory, a lot of Cherokees with the 4.0L engine came with an electric and mechanical fan. The mechanical fan, when working properly, should keep the coolant temp at 210-220 under normal operating conditions. Mine does move a lot of air, even at idle. And when I rev up the engine, it sounds like a semi!
Electric fans certainly have an advantage at low vehicle/engine speeds, particularly if a single fan is used for both the AC and the radiator. My Ram has a big-diameter clutched mechanical fan, but it ONLY cools the radiator, oil cooler, and trans cooler. The AC evaporator sits beside the radiator and has its own electric fan, so the AC doesn't increase the workload of the mechanical fan by pre-heating the air going over the radiator. You can do stuff like that when you have a grille opening the size of Nebraska...
RE the 4.0 Cherokee setup of 1 mechanical fan and 1 electric sitting side-by-side- its actually sorta best of both worlds. But its offset by the fact that the XJ has one of the most under-sized radiators I've ever seen in my life. :-/
RE the 4.0 Cherokee setup of 1 mechanical fan and 1 electric sitting side-by-side- its actually sorta best of both worlds. But its offset by the fact that the XJ has one of the most under-sized radiators I've ever seen in my life. :-/
Here is a perfect example of how electric fans are inferior in cooling abilities over mechanical. According to Flexalite website their fans for my 98 draw UP TO 5500 CFM. That's not even half the rating of the OEM fan at 12,000 CFM. According to their website, their fans draw 36 amps. 36 x12 volts = 432 watts. That's less than .6 HP. So they are supposedly saving 27hp by replacing the OEM fan with a .6hp set up...not going to cut it and Flexalite acknowledges this by recommending you NOT use an electric fan on trucks that tow over 16,000 GVW. They are essentially for dedicated grocery getters.
https://www.flex-a-lite.com/direct-fit-dual-electric-fans-for-94-02-dodge-ram-diesel.html
https://www.flex-a-lite.com/direct-fit-dual-electric-fans-for-94-02-dodge-ram-diesel.html
LOL, if an engine is sitting at idle how much cooling capability does it need? If there is zero engine load, it needs very little airflow. A mechanical fan at full lock up moves a TON of air even at an idle. They dont need high RPM which is why they are so effective on diesels. I can be chugging along at 1600 RPM pulling my 14,000 lb trailer with the A/C cranked and never rise one degree above the thermostats opening temp. Obviously on large hills it will rise a few degrees but nothing more than that.
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I think there is a lot of variation over vehicles. I would not try sticking anything in a running clutch fan on an older American vehicle. Those have a lot of torque. On the other hand, I've seen people stop a plastic clutch fan on a little Japanese car with one finger.
The way the clutch fan is supposed to work is, there is a torque breakdown at a certain rpm and torque level. This is shifted in a thermal unit by a thermostatic coil on the front that moves a valve that controls an valve in the fluid loop. But the torque characteristic is not perfect and you have significant waste of horsepower at maximum rpm. The electric fans can simply be programmed to turn of during short periods of wide open throttle the same way the AC clutch is.
They say a fan is moot over 40 mph or whatever speed. This is not true on my C3 corvette. There is so little frontal area a fan helper is needed to get enough flow at virtually any speed. I've experienced highway overheating with a worn out fan clutch in that car.
The way the clutch fan is supposed to work is, there is a torque breakdown at a certain rpm and torque level. This is shifted in a thermal unit by a thermostatic coil on the front that moves a valve that controls an valve in the fluid loop. But the torque characteristic is not perfect and you have significant waste of horsepower at maximum rpm. The electric fans can simply be programmed to turn of during short periods of wide open throttle the same way the AC clutch is.
They say a fan is moot over 40 mph or whatever speed. This is not true on my C3 corvette. There is so little frontal area a fan helper is needed to get enough flow at virtually any speed. I've experienced highway overheating with a worn out fan clutch in that car.
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Originally Posted By: turtlevette
I think there is a lot of variation over vehicles. I would not try sticking anything in a running clutch fan on an older American vehicle.
Ive done it in several diesel engines ranging from pickups to MD and HD trucks up to a 13L engine and also many older farm tractors. Its a simple and harmless test given you use something flexible like an old radiator hose. The worst case scenario is that the clutch has failed and is locked up, and it will just continue to spin and not slow down. The fan spins slow enough at idle its impossible to do any damage.
I think there is a lot of variation over vehicles. I would not try sticking anything in a running clutch fan on an older American vehicle.
Ive done it in several diesel engines ranging from pickups to MD and HD trucks up to a 13L engine and also many older farm tractors. Its a simple and harmless test given you use something flexible like an old radiator hose. The worst case scenario is that the clutch has failed and is locked up, and it will just continue to spin and not slow down. The fan spins slow enough at idle its impossible to do any damage.
Originally Posted By: jrmason
Here is a perfect example of how electric fans are inferior in cooling abilities over mechanical. According to Flexalite website their fans for my 98 draw UP TO 5500 CFM. That's not even half the rating of the OEM fan at 12,000 CFM. According to their website, their fans draw 36 amps. 36 x12 volts = 432 watts. That's less than .6 HP. So they are supposedly saving 27hp by replacing the OEM fan with a .6hp set up...not going to cut it and Flexalite acknowledges this by recommending you NOT use an electric fan on trucks that tow over 16,000 GVW. They are essentially for dedicated grocery getters.
https://www.flex-a-lite.com/direct-fit-dual-electric-fans-for-94-02-dodge-ram-diesel.html
Electric fan conversions are pretty common with the Jeep Cherokees. People would rather spend $200 on a 3 row electric fan than $40 on a fan clutch.
They just are NOT reliable off road. They get dust, mud in the bearings and you're constantly replacing fans. Plus, they don't draw enough air to keep the thing cool when it's hot out.
EVERYONE I know that uses electric fan conversions has nothing but problems.
Here is a perfect example of how electric fans are inferior in cooling abilities over mechanical. According to Flexalite website their fans for my 98 draw UP TO 5500 CFM. That's not even half the rating of the OEM fan at 12,000 CFM. According to their website, their fans draw 36 amps. 36 x12 volts = 432 watts. That's less than .6 HP. So they are supposedly saving 27hp by replacing the OEM fan with a .6hp set up...not going to cut it and Flexalite acknowledges this by recommending you NOT use an electric fan on trucks that tow over 16,000 GVW. They are essentially for dedicated grocery getters.
https://www.flex-a-lite.com/direct-fit-dual-electric-fans-for-94-02-dodge-ram-diesel.html
Electric fan conversions are pretty common with the Jeep Cherokees. People would rather spend $200 on a 3 row electric fan than $40 on a fan clutch.
They just are NOT reliable off road. They get dust, mud in the bearings and you're constantly replacing fans. Plus, they don't draw enough air to keep the thing cool when it's hot out.
EVERYONE I know that uses electric fan conversions has nothing but problems.
Not true about e-fans not being used on MD and HD. Plenty of full sized diesel buses use only electric fans.
Electric fans have kicked out the clutch fans in the half ton pickups and SUVs, and work is in progress for them to crawl further up the ladder.
The largest disadvantage of a clutch fan is lack of flexibility in placement/design of the radiator. There's only so far you can go in designing a fan shroud. If the engine and radiator do not occupy the same compartment, it's impossible.
Where failure is concerned, if the clutch is worn out,,the fan will likely not spin fast enough to cool the engine. Engine might be at zero load, but airflow is also zero, since the vehicle is not moving.
There's enough 1000+ movies cars out there using stock e-fans that it should not even be a question if the e-fans can deal with the heaviest cooling duties.
Electric fans have kicked out the clutch fans in the half ton pickups and SUVs, and work is in progress for them to crawl further up the ladder.
The largest disadvantage of a clutch fan is lack of flexibility in placement/design of the radiator. There's only so far you can go in designing a fan shroud. If the engine and radiator do not occupy the same compartment, it's impossible.
Where failure is concerned, if the clutch is worn out,,the fan will likely not spin fast enough to cool the engine. Engine might be at zero load, but airflow is also zero, since the vehicle is not moving.
There's enough 1000+ movies cars out there using stock e-fans that it should not even be a question if the e-fans can deal with the heaviest cooling duties.
Originally Posted By: A_Harman
Originally Posted By: boostedtsiawd
thing is my fan clutch is always running rather the car is cold or hot and i asked a few with the same car and they said its normal for it to be running all the time.
It shouldn't be running when your engine is cold. The clutch may be locked up and needs replacing.
The viscous clutch still has some drag when it's uncoupled and the fan will spin slowly. To test a viscous clutch make sure the fan spins at full speed when the engine is hot. As long as the engine is cold, you should be able to manually spin the fan a bit, maybe one or two turns, without it being too loose or too tight. To remove the fan clutch, usually a special tool and a very thin wrench are needed. Also, the nut is usually left-threaded.
Originally Posted By: boostedtsiawd
thing is my fan clutch is always running rather the car is cold or hot and i asked a few with the same car and they said its normal for it to be running all the time.
It shouldn't be running when your engine is cold. The clutch may be locked up and needs replacing.
The viscous clutch still has some drag when it's uncoupled and the fan will spin slowly. To test a viscous clutch make sure the fan spins at full speed when the engine is hot. As long as the engine is cold, you should be able to manually spin the fan a bit, maybe one or two turns, without it being too loose or too tight. To remove the fan clutch, usually a special tool and a very thin wrench are needed. Also, the nut is usually left-threaded.
Btw, that should have said "1000+ horsepower modified cars" but spellchecker thought differently.
Yep, and 800 HP stock cars use them too. The difference is airflow across the radiator, and even then they are running on the ragged edge at 240+ degrees. I doubt any cooling fan could sufficiently keep temps in check under full engine load and rpm if not for the directed airflow across the radiator.
When half ton pickups actually get worked they dont produce a ton of heat load like diesel engines do, and they are nowhere near the towing capacity of HD pickups. Step up to even a 3/4 ton diesel and guess what's under the hood....a belt driven fan.
I only know what Ive seen when it comes to diesel pushers but Ive worked on a handful of them and have yet to see any true electric fan set ups. Rear radiator mounts either had belt driven fans or hyd. Driven, and the side mounted radiators Ive seen (including my great aunt and uncles 2 year old DP with an 8.3 Cummins) employ a hydr driven fan. Theirs is thermostatically controlled and only runs as needed at variable speed. For a true electric fan set up to sufficiently cool you would have to run massive fan motors which I imagine would most likely require dual altenators. I bet the space required for all electric would be significantly more than hyd fans. Not sure where the benefits would be of that.
When half ton pickups actually get worked they dont produce a ton of heat load like diesel engines do, and they are nowhere near the towing capacity of HD pickups. Step up to even a 3/4 ton diesel and guess what's under the hood....a belt driven fan.
I only know what Ive seen when it comes to diesel pushers but Ive worked on a handful of them and have yet to see any true electric fan set ups. Rear radiator mounts either had belt driven fans or hyd. Driven, and the side mounted radiators Ive seen (including my great aunt and uncles 2 year old DP with an 8.3 Cummins) employ a hydr driven fan. Theirs is thermostatically controlled and only runs as needed at variable speed. For a true electric fan set up to sufficiently cool you would have to run massive fan motors which I imagine would most likely require dual altenators. I bet the space required for all electric would be significantly more than hyd fans. Not sure where the benefits would be of that.
Originally Posted By: Kira
What year, make, model and engine?
While we're on the subject, has anyone ever heard of one of those viscous fan couplings ever breaking or leaking out? Kira
Yeah the viscous clutch on my BMW failed, it stuck "on" so it roared all the time. However, the electrical fan (it has both) has failed twice now due to rust and corrosion in the motor.
What year, make, model and engine?
While we're on the subject, has anyone ever heard of one of those viscous fan couplings ever breaking or leaking out? Kira
Yeah the viscous clutch on my BMW failed, it stuck "on" so it roared all the time. However, the electrical fan (it has both) has failed twice now due to rust and corrosion in the motor.
Originally Posted By: SHOZ
If reliability is the major concern I guess you could go back to a fixed blade steel fan. Since 1996 I have had one electric fan go bad in about 300k miles of driving.
I've had problems with electric fans, a few times, but never with the fans themselves. It's always a connection, a fusible link, or a relay or some such thing that gives up the ghost.
If reliability is the major concern I guess you could go back to a fixed blade steel fan. Since 1996 I have had one electric fan go bad in about 300k miles of driving.
I've had problems with electric fans, a few times, but never with the fans themselves. It's always a connection, a fusible link, or a relay or some such thing that gives up the ghost.
Originally Posted By: jrmason
When half ton pickups actually get worked they dont produce a ton of heat load like diesel engines do, and they are nowhere near the towing capacity of HD pickups. Step up to even a 3/4 ton diesel and guess what's under the hood....a belt driven fan.
Our new Ram has both. A regular clutch type fan driven off the engine via serpentine belt and a small EFan way up front on the back of the radiator. From driving it we see the EFan only comes on when you sit for an extended period with full AC on in hotter weather.
Our fleet vans are all clutch driven, and when you're sitting stationary in a driveway running 1750 rpm you need a big fan to generate airflow under the vehicle to keep converters, etc., cool...
When half ton pickups actually get worked they dont produce a ton of heat load like diesel engines do, and they are nowhere near the towing capacity of HD pickups. Step up to even a 3/4 ton diesel and guess what's under the hood....a belt driven fan.
Our new Ram has both. A regular clutch type fan driven off the engine via serpentine belt and a small EFan way up front on the back of the radiator. From driving it we see the EFan only comes on when you sit for an extended period with full AC on in hotter weather.
Our fleet vans are all clutch driven, and when you're sitting stationary in a driveway running 1750 rpm you need a big fan to generate airflow under the vehicle to keep converters, etc., cool...
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