I thought about this a few days ago. My 1999 Ford Ranger 3.0 4×4 w/ the 4-speed automatic has an old fashioned mechanically driven fan, not the electronic fans that the Taurus had at the time. When you switch the A/C on in a car with electronically controlled fans, they automatically turn on to increase airflow through the grille and improve the cooling capacity of the system and to keep the car from overheating, particularly when you're idling.
How does this work on a mechanically driven fan, if there is such a feature at all? With it basically working on a heat-operated clutch, there doesn't seem to be a way to turn it on and off for the A/C, other than engine heat. Does the engine spin the fan enough when the clutch isn't fully engaged to keep the condenser cool?
A belt-drive fan would (hopefully) be sized for worst-case conditions. My '99 Cherokee has both a belt-driven fan with a fan clutch and an electric fan. (Many very old cars with a belt driven fan don't even have a fan clutch.)
My fan definitely can move quite a bit of air. Seems like overkill sometimes. Haha. I was trying to ask if the mechanical fan by itself has some kind of feature to engage and disengage with the air conditioner. My fan seems to always spin, cold or hot and doesn't really change speeds when idling, not that I've noticed at least. A popular mod with Ranger owners is to delete the belt driven fan and put electric fans from the Tauruses in. Apparently it saves some horsepower and gas mileage. I don't plan on doing it. I prefer a mechanical fan because it's almost fail-proof.
How does this work on a mechanically driven fan ... there doesn't seem to be a way to turn it on and off
There are different types. Modern electro-mechanical clutches are computer controlled. Your Ranger may just use a bimetallic strip actuated valve.
Good summaries:
https://help.summitracing.com/app/answers/detail/a_id/5272/~/how-does-a-fan-clutch-work%3F
https://www.onallcylinders.com/2016/11/10/understanding-fan-clutches-time-replace/
I wondered if my clutch needed replaced because it always spins, cold or hot. I never paid much attention to how fast it spins. It's never run hot, and warms up in a reasonable time, so I would assume it's good. I've never actually looked much into how they work, thanks.
If the fan clutch can spin freely without resistance it is malfunctioning. My truck was overheating and I checked everything. It turned out to be the fan clutch.
The reason that manufacturers changed from belt-driven full-time fans is that driving the fans when not needed - first couple miles, when cruising at a moderate speed, the fan uses some additional power - so to save the extra tenths of mile per gallon, they switched to clutches and electric fans.
