Cooling fan is always running this summer

the clutch-fan in my truck doesnt kick in until 200 or so.

When the car is OFF (and cold) can you spin the fan by hand?

I wonder if this is related to a problem we've been having with the AC on our '98 Z3 convertible, 2.8 litre. We cannot turn it completely off. Instead of having 0 1 2 3 4 as controls, it gives us 1 1 2 3 4, so there is always cold blowing. Other than that, it works great! Even when the outside temp is 90 to 95, the air is chilling in the cockpit.

And yes, I can move the fan by hand when the engine is off and cold.

Most cars' blower motor controls are set to run the fan at low speed all the time while the AC compressor is engaged. It's done to keep air flowing through the evaporator matrix to prevent ice from building up on it. I bet the fan will go off completely if you turn off the AC button.

Yes, it does go off if you turn off the AC.

Thanks!

Eh? It gets hot, not cold. ;-)

Nope. Evaporator gets cold...

-Fred W

Which heat exchanger are we talking about? The aux fan runs continually to keep the condenser cool. The interior fan may be switched off, as there's a probe in that heat exchanger to prevent iceing.

The AIR passing through the evaporator gets cold, the REFRIGERANT (R12 or R34) that is going through the liquid-to-gas phase-change inside it is getting hot. Opposite in the condenser.

Floyd

Yes, in layman's terms a fluid that evaporates sucks in heat; one that condenses releases heat. It's all made even more efficient and worthwhile by the latent heat step in the temperature profile of the transition. But this is getting all too damned scientific.

I dunno, as I was not the OP. I was just mentioning that evaporators get cold (and condensers get hot) in the AC scheme.

Fred W