Message text written by "Hugh Barber"
>Has anyone encountered an actual problem with putting the thermostat in
the
upper hose?.....
<
I assume you mean the electric switch that turns on the fan and not the
self actualting valve the regulates water flow. ;-)
I think it is a difference in philosophy. Most cars equipped with electric
fans use switches mounted in either the hot side radiator reservoir or in
the cooling system near the thermostat (the valve). The thinking is that
if the coolant reaches a certain point at these locations (some temperature
well above the thermostat (the valve) opeining point, there is insufficient
air flow to keep the engine cool. Mounting it in the radiator will not
detect a failed-to-open thermostat but running the fans won't help anyway.
The disadvantage to this is to get proper sequencing of thermostat (the
valve) and fan operation the engine temp will have to rise above the
thermostat opening temp and to prevent unnecessary fan operating the fan
switch setting will have to be higher to accomodate the span over which tha
valve opens (about 10 degrees F) and manufacturing tolerances in
thermostats and fan switches.
Mounting it in the return hose will turn the fans if the coolant returning
from the radiator is still hot which is an indication that there is
insufficient air flow. However this switch will need a lower set point
than the switch mounted in the hot side of the system. The advantage to
this is you can more easily detect when the thermostat goes full open (the
increased flow through the radiator along with reduced airflow will cause
the radiator exit temperature to rise sharply) and turn on the fan before
the engine temperature rises much above thermostat temperature. But at
what temp do you set it? Too low and you approach ambient temperature
under extreme conditions. Too high and engine temperature will rise too
much before the fans come on.
In a perfect world I'd put one in each location along with thermocouples to
help determing optimum set points.
Cheers
Dave
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