Best temperature range switch for electric fan?

dieseldog69 said:

Yes but you only need the fan to come on when the radiator can no longer cope with low air volumes passing through.

Mechanically driven fixed blade fans were easy, fast and cheap back in the day, upgrade to the most reliable form of cooling was the viscous coupling that locked the fan once it reached a certain temperature, a knock on side effect that was a bonus for turbo intercooled engines was mechanically driven fans helped with intercooler temps when running at slow speeds as air was continuously being drawn through the intercooler.

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The Mad Hat Man said:

Bugger me... I am not explaining myself well.......
I meant that the primary purpose of a cooling fan was to assist in keeping the water temp below a critical threshold and, as such, you need to be monitoring the temperature where that critical threshold is likely to be reached, not after a cooling system that may, or may not be efficient.
For example, if the cooling system is such that you get a 5 dog drop between engine water outlet and return then that isn’t too bad, but if there is a 30 dog drop, then the cooling fan will never switch on until the engine has suffered a severe overheat. You can overcome this by setting the fan switch on temp to allow for the temp diff, but as the cooling efficiency deteriorates with age, this will affect when the fan switches on, compared to coolant outlet temp. That is why I maintain it is better to monitor the engine temp where it is most critical - ie combustion chamber water jacket. Being in mind this is difficult to achieve then the water temp should be monitored as close as possible to that critical area - normally this is where the coolant exits the engine at the top.

Sermon complete .

Click to expand...

The Mad Hat Man said:

Bugger me... I am not explaining myself well.......


Sermon complete .

Click to expand...

The Mad Hat Man said:

Bugger me... I am not explaining myself well.......
I meant that the primary purpose of a cooling fan was to assist in keeping the water temp below a critical threshold and, as such, you need to be monitoring the temperature where that critical threshold is likely to be reached, not after a cooling system that may, or may not be efficient.
For example, if the cooling system is such that you get a 5 dog drop between engine water outlet and return then that isn’t too bad, but if there is a 30 dog drop, then the cooling fan will never switch on until the engine has suffered a severe overheat. You can overcome this by setting the fan switch on temp to allow for the temp diff, but as the cooling efficiency deteriorates with age, this will affect when the fan switches on, compared to coolant outlet temp. That is why I maintain it is better to monitor the engine temp where it is most critical - ie combustion chamber water jacket. Being in mind this is difficult to achieve then the water temp should be monitored as close as possible to that critical area - normally this is where the coolant exits the engine at the top.

Sermon complete .

Click to expand...

jamesmartin said:

if you were fitting a temp sender in bottom hose it would need to be a lower temp operating one, whatever condition of rad the flow from the rad needs to be under a certain temp for cooling to take place,just as the temperature in any part of the engine is,and bottom hose is where thermostat is now commonly fitted,but if you wanted to use the highest temp reached first as the criteria you fit sender at the rear of no 4 cylinder

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