temperature sensor IN radiator => electric fan

hello folks

got some questions:

why do some people put there temp. sensor (for the electric fan!) in the
hose that comes from the thermostat and leads to the radiator? => the
hot waterside

why do others put the sensor IN the radiator or in the hose that leads
to the waterpump? => the cooler waterside

Volvo puts it in the radiator (so the cooler waterside)

Are all the volvo sensors the same? (partnr:1274962)
for all the 960/740/940/850 and other models?
do they all fit in the radiators?

they open at 96°C and close at 92°C
Are there some other degree scales? (later open/close, or earlier?)

i'm planing to put an E-fan into my 240
have a 3-row radiator (with a rubber piece where the sensor should
come) and a 87°C thermostat

where would you put the sensor?

who has some advice here?


greets and tia

kwijlebabulus

 

I can see problems with either approach if an on/off fan control is used:
1) if the sensor is at the radiator inlet then the fan could be running when
it is not needed as airflow without the fan might be enough to cool the
coolant suffiently and the fan running would "over cool" it. There would
also be a large time delay in responding to the cooling also as the cooled
water would have to make it around the engine and back to the radiator.

2) If the sensor is at the radiator outlet then the fan does not come on
until the coolant exceeds the desired temperature. The coolant will then
cool down below the desired temp and the fan will constantly be cycling on
and off.

With an on/off control I think situation 2 (at the radiator outlet) would be
preferable as this would respond more quickly to cooling needs. This type
of control is also very cheap, if not real precise.


Something a little more esoteric:
(the controls engineer in me just has to present this ;-)
If the electric fan has a variable speed control (other than just on/off)
then a sensor just on the outlet of the radiator could be used vary the fan
speed proportional to the temperature of the coolant. The controller would
turn the fan on at minimum speed at some temperature (maybe right at the
desired engine inlet temp) and run faster as the coolant temp increased --
reaching full speed well below maximum allowed engine inlet temp.

The components to build a variable controller are actually pretty cheap.
The problem is determining the parameters of the control problem and the
degree of variation in the parameters under different operation conditions.
Seems like it might be a good problem for a "fuzzy logic" type controller
and use of a sensor on both inlet and outlet. Then the controller could be
fairly independent of the exact parameters and self adjust to changes in
operating conditions.

This more advance controller would give a much more consistent temperature
control to the engine but is probably overkill. Option 2) above is the best
bet.

Bob

 

hello bob

do you have an email adress that works?

thx kwijlebabulus

 

Bob

Your forgetting the engine thermostat, you do not have to worry about
overcooling ( unless you freeze the rad. core) as the engine thermostat
determines the operating temp regardless of the rad. temp.


Harold

 

Variable speed controller: www.dccontrol.com