A fairly simple question that isn't explained in the Haynes book, et al.

I thought that it's supposed to disengage when the air coming through the radiator is 'cool?' Gives more HP while you are at speed, then engages when not rolling along?

My fan turns all the time, even right after you start the cold engine.

thx

The fan clutch keeps the fan from spinning to fast so it won't break up into a million pieces.

Vicky

Ok...

So if you stomp on the gas, the clutch will slip and the engine will rev easier.

Does it still slip at WOT, when you're moving?

What's "WOT", With Out Throttle?

Vicky

It should turn as you start your car with a cold engine, if you rev the engine a few times into the higher rpms, it should for the most stop and not give you the jet engine sound any longer.

Mine must be siezed up then.

OL...

Originally posted by dattozed

It should turn as you start your car with a cold engine, if you rev the engine a few times into the higher rpms, it should for the most stop and not give you the jet engine sound any longer.

An electric fan is thermostatically controlled and will click on when called for. The fan that's attached to the pulley should run all the time........if it doesn't you gotta problem.

Vicky

Then we are kind of back to the original question...

The fan clutch works on both RPM and temperature. It slips at higher RPM and at lower temperature. It will always spin some. So, if you are idleing in traffic, it will engage as the air coming through the radiator gets hotter, and slip some as it cools off. If you rev the engine sitting in traffic, it will be engaged due to the temperature, but will then slip some as the engine speed rises. As the car starts moving, the temperature of the air moving through the radiator drops, and thus the clutch starts slipping due to lower air temperature, as well as the rising engine RPMS.

I think it's mostly supposed to disengage over about 2500 RPM, but it will always turn some.

Here's the description of the fan clutch's operation out of the '78 factory manual.

Isn't that what I said? No sense in turning the fan when you're on the highway.

Originally posted by TomoHawk

Isn't that what I said? No sense in turning the fan when you're on the highway.

Yup. I just like to hear myself type!

Some clutches lock up all the time, and then you get the airplane sound effect as you accelerate. Mine (on my '78) currently won't engage at all, and thus I overheat if I sit in one place for very long. Got to get that replaced now that warm weather is here!