My Mom has a 1995 Mercury Grand Marquis with a radiator/engine overheating problem. The temperature skyrockets on occasion during slow, stop/go driving. Upon stopping and opening the hood with the engine still running, I see that the water pump belt-driven cooling fan is not turning(the smaller aux electric fan is running[while AC is on]) and the belt is not slipping.
I've been told my various shade tree mechanics that there is a clutch that gets the fan blade turning, but as to how the clutch is activated, I get varying stories. Some say the clutch is centrifugally activated due to the RPM of the drive belt. Some say the clutch is electrically activated by a fan clutch switch but the location of said switch is not known...some say in the radiator, some say in the thermostat, some say in the engine block.
If there is a switch, I'm thinking it's thermostatically activated, but that's a guess on my part. That stuff about centrifugal activation kind of has me puzzled.
I'm used to GM vehicles' electric cooling fans, having had to replace one on a Celebrity, and two on a Century. Voltage present to fan, but fan doesn't work...bad motor. No voltage to fan motor, switch problem. Simple.
I'd appreciate a "How it Works" tutorial on a, for lack of a better name, mechanical cooling fan. Thanks for any information or insight you can provide. Also, if you know whether it's the clutch or switch that is the more common culprit.
Danny getting hot in Yorktown, VA