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Discussion Starter #1 (Edited)
Just wonder if anyone has converted a manual fan and fan clutch to a electric only fan. My 99 Silverado xcab 5.3 usually get about 14.5 mpg in town but this summer we have had over two months of 100+ degrees heat here in Texas. I notice that the fan clutch is engaged mostly all the time now hence my fuel mileage has dropped to 12.5 mpg. I believe this is the cause. Of course the super hot air temperature doesnt help either. On the highway its the same about 19 mpg.
 

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the electric fan would get you another MPG, as for the cost you can do it cheaply, there is a write up in the how to section using a dual fan out of a ford taurus/mercury stable from a 3.8 V6 and then using a relay
 

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I did some math and came up with the following... Gasoline-$3.50 gal., 16MPG and 25 gal tank will get you 400 miles and cost 87.50 or 21.87 cents a mile.
Go to 16.5MPG and 412.5 miles per tank and your cost per mile drops to 21.2121..... a difference of .6 cents a mile or $2.40 a tank. The math may not be perfect but it is close. The more gas costs the better the return and the higher your mileage is to start, a .5MPG gain will return a smaller % gain in savings. If whatever you did cost $200 and it gained you the .5MPG ALWAYS (not likely) then it would take about 83 tankfulls to break even. I would suggest to anyone doing improvements to save money is to do the math and then decide the true costs.

These thoughts seem to be a sound reasoning BUT I have only myself to check with at the time of this post.
 

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I see it as this, if GM has finally done it as a factory standard on the NNBS trucks then it must be worth it in the fight on gas and MPGs
 

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I would agree with vncj96. If/when my fan clutch gives up I will likely spend the money on electric fans. I beleive that the ecm has an output for a fan relay but need to verify that. Every bit helps. Get rid of the excess junk you may be hauling around and keep the tires inflated correctly...free mpg improvement!

Anybody know of an online MPG calculator or cost per mile calculator that takes into account gas price and vehicle operation costs?
 

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Discussion Starter #8
Well I can get the parts fairly cheap from my friend who owns a salvage yard. I figure anything that takes money away from the OPEC is worth doing.
 

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I notice that the fan clutch is engaged mostly all the time
What do you mean "mostly all the time"?

There are two parts to a fan clutch. There's a viscous coupling that's intended to freewheel the fan at lower temps and higher speeds, and there's a bimetal thermostat that locks up the clutch when it reaches the high temperature limit. When you first start up on a cool morning, the fan shouldn't be running at full speed when you run up the engine. If it is, the clutch has failed and you're going to be pouring a whole lot of power into the fan unnecessarily. So much power that it will definitely affect your fuel usage.

There's no good reason to replace a properly functioning mechanical fan and clutch with electric fans. You'll never recover the cost. Electric fans aren't the panacea that everyone seems to think they are, anyway. They have losses of their own (motors get hot and waste power), not to mention the inefficiency of the alternator itself. It's not all that great in converting mechanical energy into electrical energy. The reason for electric fans in the newer models is that they can be controlled directly by the engine computer and integrated into the engine, transmission, and a/c systems. If you could achieve this level of control with an aftermarket system (which you can't) then maybe it might be worth the cost to switch over.

Anyway, test the fan operation on a cool morning. If it runs unnecessarily, just replace the clutch. It's by far the lowest-cost alternative.
 

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i have em (dual electric) in my truck. they dont run to much, but the cost to change em out vs. savings is so close that its not worth it baring some sort of major failure in the mechanical fan. one thing to consider tho is the ease of working on the engine without a mechanical fan, dual electric = more room to work. easier belt routing and so on.

just my .01 worth.

Alex
 

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I am thinking of converting to electric fans, too. As the posts seem to indicate the validity of the First Law of Thermodynamics, that thermo energy can not be created nor destroyed - only converted, the choices are labor the engine with the clutch fan or labor the alternator with the added electrical load. Both systems are temp controlled so that seems to be a wash. The electric fans are said to be more efficient, especially dual fans, and have to run less?? But, then there is that First Law again!! I have not made up my mind, but racing colleages say the electric fans save noticable horsepower??
 

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Discussion Starter #12
What do you mean "mostly all the time"?

There are two parts to a fan clutch. There's a viscous coupling that's intended to freewheel the fan at lower temps and higher speeds, and there's a bimetal thermostat that locks up the clutch when it reaches the high temperature limit. When you first start up on a cool morning, the fan shouldn't be running at full speed when you run up the engine. If it is, the clutch has failed and you're going to be pouring a whole lot of power into the fan unnecessarily. So much power that it will definitely affect your fuel usage.

There's no good reason to replace a properly functioning mechanical fan and clutch with electric fans. You'll never recover the cost. Electric fans aren't the panacea that everyone seems to think they are, anyway. They have losses of their own (motors get hot and waste power), not to mention the inefficiency of the alternator itself. It's not all that great in converting mechanical energy into electrical energy. The reason for electric fans in the newer models is that they can be controlled directly by the engine computer and integrated into the engine, transmission, and a/c systems. If you could achieve this level of control with an aftermarket system (which you can't) then maybe it might be worth the cost to switch over.

Anyway, test the fan operation on a cool morning. If it runs unnecessarily, just replace the clutch. It's by far the lowest-cost alternative.
No the fan clutch is not engaged when the engine is cold. Consider that here in east Texas we have had over 70 straight days of well over 100 degree temps. Many times the heat index has been as high as 115 degrees! So that while driving around town with ac on the clutch is engaged nearly all the time as I can hear the fan roaring. It doesnt do this at night.
 

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Sound like the clutch is fine. Doing a suburb job. Just becareful with the electric fan's wiring. Previous owner installed an electric in my Sonoma GT, 4.3, hell of a hot rod but the heat wave this year really taxed it and the inline fuse holder melted. Fuse never blew but it was the wire between the fuse and fan come loose inside and was arcing. I noticed the fans not working and checked the fuse and found the damage. It was right after parking it and I hooked up a straight conection and left it for 20 min and the fan never kicked on. Looks to me something else went too because even after market fans run when the key is off because they have a thermostat connected to a switch directly connected to the battery. But if one does go to an electric fan, maint costs come into play. You do have gains going to a electric fan but hang on to the mechanical one incase your electric one goes out.
 

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OEM E fans are computer controlled buy coolant temp. , a/c demand, and vehicle speed. Over certain speeds computer turns off fans.
Fans must be on for a/c operation to cool the condensor.
Most E fan kits you see are for performance applications, no a/c needed or used there. Other than the fan clutch setup a flex fan is the other option.
Street driven truck, stay stock, it's tried and true to keep you rolling.
 
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