This way the fans are working in conjunction with the thermostat, both attempting to regulate the temperature of the coolant exiting the engine block.
I've answered the other questions in sticky #2.
quote:
Originally posted by George P:
... My solution to resolve the issue of the Pantera's constantly running fans is to control both fans with one fan switch so the fans will turn off and on simultaneously; the fan switch shall have a very specific temperature setting allowing it to start and stop the fans in the middle of the operating range of the thermostat. The mid-point of the fan switch operating range should therefore compliment the mid-point of the thermostat's operating range as closely as possible. The fan switch should be located in the radiator's inlet tank (the lower tank) so as to sense the coolant temperature regulated by the thermostat ...
... These considerations are reflected in the switches I've recommended below. Here's the part numbers for name brand fan switches with M22 threads:
Manufacturer...Part Number.........Switch Setting........Thermostat
Intermotor......50190..................100°/95° ..............195°F (91°C)
Intermotor......50104..................97°/92° ................192°F (89°C)
Intermotor......50200..................92°/87° ................180°F (82°C)
Wahler...........823.959.481.F ......92°/87° ................180°F (82°C)
...
To understand the engineering behind the selections, you have to understand the operating characteristics of the two devices.
An 82°C thermostat (180°F):
- Begins opening somewhere between 78°C and 82°C. Thus a portion of the coolant recirculating through the engine begins flowing to the radiator.
- Is open midway somewhere between 85°C and 89°C (87°C is the mid-point within the range of mid-points). Unique to the 351C in its day, coolant bypassing the radiator and recirculating through the engine is blocked-off at this point.
- Is fully open somewhere between 92°C and 96°C. At this point the maximum amount of coolant is capable of flowing both through the engine and to the radiator. But the actual flow rate is limited by engine rpm because the coolant pump is crankshaft driven.
- Has an operating range spanning 14°C on average.
A fan control switch rated 92°/87°:
- Starts the fan(s) at 92°C, the earliest possible temperature the thermostat may reach full open. For the coolant to have reached this temperature even though the thermostat is almost fully open, it is obvious that the amount of coolant flowing is insufficient to handle the engine's heat load.
- Stops the fan(s) at 87°C, when the thermostat is once again in the middle of its control range, and coolant temperature is once again capable of being controlled via modulation of the coolant flow rate.
- Has an operating range spanning 5°C, 36% of the operating range of a thermostat. Thus the fan switch can operate "within" the operating range of the thermostat.
Thus the fans "start" only when the heat load overwhelms the cooling system's ability (via the thermostat) to control the temperature of the coolant without their assistance, and the fans "shut-off" when conditions return to normal, and the thermostat is once again operating in the middle of its range.
-G