stupid question about the engine fan

chevy4x4trucks · April 24, 2002

I was changing my oil today and couldn't help but notice that the engine fan was always spinning when the truck was just sitting there idling. Should this be? It seems pretty stupid and power robbing to always be spinning. Just another weird observation by me.

silverado man · April 24, 2002

I believe since the truck is sitting there isn't enough air movement to cool the coolant so the fan has to be on. The fan should have a clutch on it so when the temp. is right than clutch shuts the fan off. At least thats my understanding.

MountaineerTom · April 24, 2002

Silverado Man's right, the fan spins all the time when idling. That's the beauty of electric fans, they turn on at a certain temp, or you can wire in a switch to turn it on manually.

chevy4x4trucks · April 24, 2002

all the more reason to hook up an electric fan. I'll probably do that eventually and get rid of the power robbing clutch fan. It just struck me as odd that it seemed to always spin.

Kansas Kid · April 24, 2002

Thermal clutches have a bi-metal coil spring at the front that reacts to temperature, the hotter the air temperature off the radiator the more lock up is applied. Usually this clutch is only working at idle speed, as the vehicle moves through the air the bi-metal spring cools down releasing the clutch. Thermal clutches use silicon as an internal lubricant because of its constant viscosity under wide temperature variations.

With that being said, how much power do you think is necessary at idle? Thats about the only time it will come on in your application since you don't tow anything. I could see spending the money for an electric fan if your fan was engaged constantly at highway speeds (and trust me, you will know when it engages), but why spend the money when it really isn't robbing you of power all of the time?

I forgot some things I wanted to say. Do you wish to upgrade your electrical system as well? Those electric fans suck alot of juice, and the stock alternator will not handle it well at idle (once again, about the only time it will be on). It should also be noted that electric fans are not recommended for heavy towing applications. I don't know why, but thats what the manufactures say.

VikingZ · April 25, 2002

Ditto what Kansas said.

silverado man · April 25, 2002

Thermal clutches have a bi-metal coil spring at the front that reacts to temperature, the hotter the air temperature off the radiator the more lock up is applied. Usually this clutch is only working at idle speed, as the vehicle moves through the air the bi-metal spring cools down releasing the clutch. Thermal clutches use silicon as an internal lubricant because of its constant viscosity under wide temperature variations.

With that being said, how much power do you think is necessary at idle? Thats about the only time it will come on in your application since you don't tow anything. I could see spending the money for an electric fan if your fan was engaged constantly at highway speeds (and trust me, you will know when it engages), but why spend the money when it really isn't robbing you of power all of the time?

I forgot some things I wanted to say. Do you wish to upgrade your electrical system as well? Those electric fans suck alot of juice, and the stock alternator will not handle it well at idle (once again, about the only time it will be on). It should also be noted that electric fans are not recommended for heavy towing applications. I don't know why, but thats what the manufactures say.

Well if you want to get technical that what it is.

bassdog · April 25, 2002

I disagree with Kansas a little. From the time the key is turned on and your engine is running you are losing power. The "lag" from the belt pulling and pushing all your accessories is making the engine work harder, and robbing power. Without getting technical, here is an example of what I am talking about:

Take two identical trucks - one with and one w/out A/C. The one w/out a/c will logically run "better" than the one with. This is the same with or without the fan. You may need to upgrade your alt., but you are removing that "lag" from your belt system...thus more power.

Just my view on it, I may not be correct, but this has always been the way I understood it. If the electric fans didn't do anything, there wouldn't be a market for them.

Shaners · April 25, 2002

Not this matters, but all front wheel drive cars with transversly mounted engines run at least 1 electric fan. I've had several that run 2 fans... I can't imagine that a 4-cyl car with an electric fan/s would have a bigger alternator than a fullsize truck...

Granted they have a smaller radiator than the truck and most likely less water to cool, but the difference can't be that big...

Victory Red · April 26, 2002

Think about this. Transversly mounted engines have to run electric fans. It's kinda hard to cool the radiator with a belt driven fan pointed out the side of the car. Also, I would guess that the extra load on the alternator from running elec. fans is about the same as the load on the engine from a belt driven fan (when the clutch has activated it). So IMHO, it's 6 in one, and a half dozen in the other. Keep your belt driven fan and save yourself the time, money and headache of installing elec fans. I doubt you will notice any performance gains by this mod anyhow.

JMTC

VR

95Yukon · April 26, 2002

All the tests I have seen show dyno results which add 12hp and 15 lb ft of torque by going electric, and a 2-3 mpg increase in mileage. It also takes some strain off your water pump bearings, which makes it last longer. The amount of "drag" on the alternator to run the fan is not nearly as much as the old fan itself, which even when "disengaged" spins at about 30% of the engine speed. It slows down, but still is engaged and causing a lot of drag even when it is not needed. Anything putting drag on the engine, even at idle, is going to cause it to consume more gas.

True, the electrics usually only come on when sitting and idling and it starts to get hot (or if the a/c is on) but you may want to check out flex-a-lite.com, they have a new item (260 or 280?) fan for the new trucks which now has a 2 stage variable voltage going to the fans, so they run at 60% speed for a/c and cooling when needed, then ramp up to full speed if the temperature sensor says its getting too hot. http://www.flex-a-lite.com/auto/270_280.htm and

http://www.flex-a-lite.com/auto/Applicatio...e/fulltruck.htm

I'm getting the new controller unit for my 250 kit, and aside from the draw on the electrical system, I think the electric fans are great. The new controller will keep it to a minimum for draw.

Smaller cars with electric fans don't all have big electrical systems, but the fans are about the size of the one cooling my computer chip.

All the newer trucks already have a higher amp output alternator than mine did (before I put the high output on) and even the old 70/105 amp handled it fine. (now 80/120)

There is also a knob on the control box that lets you control the temperature the fans turn on. Takes about an hour to install, but they are somewhat pricey.

My .02

MountaineerTom · April 26, 2002

All the tests I have seen show dyno results which add 12hp and 15 lb ft of torque by going electric, and a 2-3 mpg increase in mileage. It also takes some strain off your water pump bearings, which makes it last longer. The amount of "drag" on the alternator to run the fan is not nearly as much as the old fan itself, which even when "disengaged" spins at about 30% of the engine speed. It slows down, but still is engaged and causing a lot of drag even when it is not needed. Anything putting drag on the engine, even at idle, is going to cause it to consume more gas.

That's the same info I've always read/heard.

gandolphxx · April 26, 2002

My research agrees with all of that, one small issue remains:

Why do they not reccommend electric fans for heavy towing?

Is it because of the excessive use in a high load situation?

95Yukon · April 26, 2002

I haven't actually heard of them not recommended for towing..I don't know why it would be bad, since they flow more air than the stock fan when flow is needed, so it would be more efficient if anything. At low speeds and heavy loads, they may run more often, but mine runs full time when the a/c is on, (as do all electrics on cars with a/c -for airflow through the a/c condenser) which is almost all the time here in the summer, and no problems at all.