learn me fan clutch

So all I know about them is that they are supposed to freewheel when cold and at highway speed.

How do they actually work?

How do you test them?

Are there different specs, and how do you choose the right one?

you replace them and then in 2-3 weeks you replace the complete assembly with the motor and clutch assembly

The BMW test is to stick a rolled up newspaper into the fan when cold. If it stops, the clutch is working; if it shreds the paper, the clutch is locked up and needs to be replaced. Personally, I just replace them every 100k miles and call it done.

Is this in the El Camino?

Yes. Well, this one at least. Clutch and fan from a 93 blazer.

But im thinking of doing away withthe electric fans in my duster as well.

And, with the amount of random crap I work on, I should probably learn about these things. Only thing I know other than what I posted is that when the fan roars like a banshee ans wont spin independantly of the water pump, the clutch has gone to hell.

If you are talking about traditional American design, there should be next to no slop in the bearing. With the engine off, it should spin reasonably free, but with enough drag you can't make it do more than about one revolution with a single spin.

The easiest test in a daily driver is to drive and listen. My old Dakota, you couldn't miss. Towing the trailer on a hot day, every few minutes I would hear it spin up and pull a monster amount of air, then 30 seconds later it would settle down again.

Listening to that made me really question the use of electric fans on the highway in that situation. No way an electric fan could pull that much air..

They are black voodoo and should be avoided.

For a stock vehicle, some engineer making way more money than me figured the clutch had to lock up at X temp and everything would be fine. Start making things not stock (ElCamino airflow vs. 93 Blazer airflow for just one example) and all of that engineer's calculations go out the window. I'm sure they can work just fine, but that would be more luck than anything. Somewhere someone has a list of lockup temps for the clutch for a 93 Blazer vs. a 92 with the tow package, etc. That would still require some trial and error for your particular application.

I like the tunability of electrics. Running a bit hot? Put a lower temp switch in. Running REALLY HOT in traffic? Jump the relay to high (try doing THAT with a clutch fan)!

That being said, if you already have one you might as well try it. If it IS locked, I'd skip ahead to an electric setup.

If you have to replace any part of a mechanical fan setup, it's usually best to switch to an electric fan. That's what I did when I snapped a couple blades off my sammy's mechanical fan in the mud.

I had a direct drive fan that had smooth curve blades that were supposed to flatten out at high speed, reducing drag. At idle it would suck a paper to the grill and there was not a pan connecting the radiator to the grill, you could see the ground.