electric fan thermostat switch

[brianstrange]

In the lower hose or cooler side of the radiator does seem to me like it would delay the fan response to a change in condition. Maybe that's on purpose?

It would if the fan temp sensor has the same temp trigger on both ends, right? It would also allow warmer water into the engine.

 

[ntsqd]

Not understanding what you mean by "same temp. trigger on both ends".

The way that I see it some desired operating temp is determined, and let's say that steady-state operation is happening where the radiator can handle the needed cooling without the fan. Then something changes to increase the coolant temp, and now the fan is needed. A sensor in the upper will see that change first, there will be some lag time before a sensor in the lower will see the change.

 

[pbwcr]

So the E fan meant to replace the mechanical fa (Mfan). The M fan operates all the time with the goal of keeping the rad coolant close to ambient air temp. As we all know that much cooling is not needed and is why many M fans have a temp sensitive clutch design. Very reliable, but still not as efficient as a proper design for an E fan.
Maybe the sensor for the E fan should keep the rad at a temp above the ambient (like the clutch fan), but still below the T stat temp? That means it is good to have an user adjustment for the control temp regardless as to where that sensor is located.
(Aside-- I cannot believe a fixed T sender will achieve our goals - - way to many variables?).

I do not have a vehicle that came from the factory with a rad E fan so I do not know what the oem strategy is or where their sensor is located. To get better data someone has to give correct input on OEM setups.
Thanks for reading my blabber, PaulW

 

[ren71]

I vote for upper. if you get a bad tank of gas or your timing is off and the engine starts pinging and the the head/water temp spikes you want the fan to kick on as soon as possible. I would want the sensor to detect the temp spike before it has to go through the radiator. This also makes sense for the gauge sensor

 

[ntsqd]

With a sophisticated control system I can see wanting a transducer on both sides of the radiator. Could then program for max delta-T allowable before the fan comes on without worrying too much about actual temperature, but could also set a hard limit for either sensor's signal that turns on the fan regardless of delta-T. It should also know when things like A/C are on, because then it could adapt favorably. Such a system should also have PWM capability for variable fan speed too.

That ain't us, or ain't most of us anyway.

Back to the OP's question, I think that as long as the adjustment range of the sensor will allow it that it won't matter where you put it. If it doesn't have that much adjustment range then you need to look at where those temps will be and place it there. Most likely that means near the t-stat. As too which side of the t-stat (engine or radiator) I don't think that it will matter much, but given a choice I'd choose the engine side as I think that this placement will result in less up/down temperature cycling.