A centrifugal clutch fan disengages the faster it spins

A viscous, fluid clutch operates on temperature of the air moving thru the radiator, so if the engine is running hot in traffic it kicks in, at freeway speeds with an inrush of cool air moving thru the radiator it will disengage to free up the engine.

My personal vote is towards an electric fan set-up. Besides the fact it frees up HP and will marginally give better gas mileage it's been tried and true for decades. Millions upon millions of cars have been built with electric fans and you'll be hard pressed to find any today that have a belt driven fan. I equate to most pick-ups having belt fans today just due to the fact they are inline with the radiator.

How many belts have I replaced in my lifetime? Too many.

How many electric fans? None.

My 74 truck by the end of Spring will have an electric set-up.

josh

Josh

 

I agree with Josh- my personal preference is electric. 1. If you lose a belt, you dont have to worry about cooking your engine 2. Most electric fans are very well contained and there is a less of a chance of getting hurt/maimed when working in the engine bay while the engine is running(timing, idle adjustments, etc)....but thats just my 2 pennies worth...

 

Move into the modern era and go electric. Yes make sure that you wire it correctly and you will be very happy. Nobody seems to mention how much smoother the ride is without that energy wasting direct connect fan. I too run a 2speed fan I pulled from the junk yard. It works great on my 360/4v 73 truck. Eventually I want to add an electric water pump setup so that they can cool the thing down after it shuts off.

 

It has to be 2 speed fan. The 2 speed fans will have 3 wires. One is ground, and the other 2 are for +12 volts.

 

10-4 as long as everyone posts where they got their set-ups from it should all be gravy!

Josh

 

As far as it running smoother...I had to double up on the rubber washers between the radiator and the fan in order to reduce the vibration the fan caused running. It was quite noticeable...much better now. I can hardly feel it running at all.

 

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I plan to use 2 fan switches that are mounted inline with a heater hose. Only 1 wire of the fan can have +12 volts at a time, so here's a diagram I made of how I'm going to wire it so that only 1 wire will have voltage. The fan can not run with the key off when wired this way (saves fingers).

 

My electric fans have been in for 12 months and have worked a treat. got them at the wreckers and had a temp sender put in the radiator when i installed it. Ill put some pics in my gallery.

 

That was just what I was looking for.

Rick.

 

Bullitt390 explained how the clutch fan works, but i want to add how flex fans work so you would understand the differences.


A flex fan "sucks" (it's actually pulling,) most of the air at idle. When the RPMs increase the blades of the fan, "flex" flat so there is less load on the engine, but this decreases the air that is being pulled through the radiator. So the higher the rpms, the less efficent the flex fan is. At 3000RPM a flex fan is pulling less air than it would be at idle. This is bad, especially if you are climbing a hill at 20 MPH, at high RPMs.

A centrifugal Fan Clutch, as Bullitt390, stated disengages the faster it spins, or the higher the RPM, however, it is better than a flex fan, and here is why. The fan is solid, and does not flex. Also the way the clutch is designed it's pulling at least the same amount of air at idle as it is at higher RPMs unlike the flex fan. In other words the fan is just as efficient at idle as it is at 3000RPM, pulling, aproximately same amount of air, and actually just a little more air than idle, not less like the flex fans tend to do. It also frees up horse power on your engine as well, and saves you gasoline over the flex fan.



A viscous, fluid clutch fan, is even better yet. As Bullitt390, described, because it is temperature controlled. It also has a solid fan blade. The hotter the engine gets the more air it pulls untill it locks, matching the engine rpm. Great for cooling as it will cool more the faster the RPMs with it engaged. With it disengaged it frees up the horsepower on the engine saving gasoline. However with it engaged fully it will use more horsepower and gasoline than either the centrifugal fan and flex fan. When you average it out though, it equalls about the same horsepower usage as a centrifugal clutch fan.

However when Bullitt390, says that he likes electric over either clutch fans or flex, because of the belt, this confuses me. If you go to electric, you would still need the fan belt to operate the water pump. Therefore you are not eliminateing the belt, and you still have to change it anyway at regular intervals.

 

I want to state that I do not currently have electric fans on either my 74 or 76 trucks, neither does my 2005 F250 with 6.0 diesel. My 2004 Nissan Maxima has twin electric fans.

I think overall, electric fans cool better, run quieter and have less strain on the engine than a belt driven fan. As evidenced in that link I provided.

Another is I would tend to think that with no fan strain forced onto the belt it will last longer and also put less stress on the waterpump snout, which is the primary cause of water pump failures.

Another is, in the case of my 74 truck, once I am finished with the paint and other various things it "might" get driven 2000 miles for an entire year. So I am not concerned with any fan motor failures. With a truck that gets driven 10,000+ miles I would possibly think otherwise.

But take in point between my two old trucks and my work truck, plus my previous work trucks, a 2001 with 7.3 and 2003 5.4, I changed a lot of belts. Annoyingly so.

The Maxima get churning away undaunted, as did my Ford Taurus and old Plymouth Colt.

Out of belt driven fans, I do not believe a person could beat an OEM viscous style clutch fan and then a centrifugal style and then OEM fixed blade.

The Flex-a-lite flex fans have a well deserved reputation of creating cooling problems, not helping any.

Josh

 

I used ford windstar fans (dual 2 speed fans), I think they were 1995+
for a temp switch I used a Nissan 300z non turbo sender that screwed into the rad petcock location
fans only cycle when the radiator is unable to cool without assistance
I went overkill on the relays after hearing horror storys of failures, so I used a 70 amp relay on one circuit and a 40 on the other
wired a 3 position switch in the cab on the ground side of the relays that can either gnd to chassis to trigger the fans on constant, center is fans off, last post is gnd through the temp switch for automatic operation
currently only running the one speed as I look for a NC/NO relay that has a high amp rating so I can use one relay for on/off and the second one can trigger the high speed of the fan when wired in series

 

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m j, what year Nissan was the sender from? And is it a 2 speed sender or a single speed?

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nothing to add - just subscribing!

 

gimme a sec here I will go look it up.
I found it in the illusrated Neihoff parts book
single speed and IIRC it was 1985 but I will verify it.
Neihoff has a great site that shows you pics of the products etc but part details are found in the literature...

edit... yup it was 1985 300zx non turbo- niehoff p#TS25461 comes on around the 189° to 199° mark
I was gonna trigger the high speed from the upper thermo housing but havent done that yet

http://www.niehoff.com/catalogs/nie_bgbulk.aspx
enter the part number there to see it, if the link works