Since this is an adjustable controller (flex-a-lite 31165-VSC) I think I am going to try doing the intake probe anyway. My thinking is that will let me monitor the temperature close to my engine (since that is what we are wanting to cool) and since its not just an on/off controller, I should be able to adjust things so that its not on 100% of the time.

I'll know pretty quick if Its working like I want or not, and if its isn't it will be simple enough to pop in the radiator probe, then post about my change so Drew can say "I told you so"

 

you won't catch me saying that..

just remember, though, that the exchange (radiator) is just as much a part of your cooling system as the lowly radiator cap or the water pump.. it should be the first consideration for monitoring, as that is where the heat exchange takes place..

 

lets put it this way...why is the gauge sensor port in the coolant and not on a probe for the radiator? personally, i'd want it in the coolant, after the thermostat. once the thermostat opens for its set opening temp, fluid will start to flow through the upper radiator hose. only then will it make sense for the fans to come on. if you put the probe in the intake manifold, and the sensor picks up that the fans need to come on, but the thermostat hasn't opened yet, you're not cooling anything.

i guess it can work either way. i'd just assume you'd get more accurate and reliable results from actual coolant vs. surface temp

 

Temp sensors for the gauges are before the thermostat, as you want to know what temp the ENGINE itself is...... and if it is overheating. If the thermostat failed closed, your gauge would never indicate there was a problem, and your first hint would be when the engine failed...... not a good scene.

Cooling fan is to cool the coolant in the radiator... so, testing temp in the place that you are actually wanting to cool is the hot ticket.

 

i understand why the gauge is where it is...i was just pointing out the difference between being in coolant itself and not strapped to something

 

I had a pretty blue coupler spiced in on the bottom tube one time....

Then, I dipped a probe in the extra temperature port on the air-gap another time..

I ended up shoving a probe through the radiator in the end...

fwiw, here is how I came to do that:

consistency.. if the cooling system is healthy, there will be a region on the radiator that hovers within a 3~4* parameter.. I selected a region in the neighborhood of 185* using the IR gun.. It is likely 3" from center on the radiator (vertically speaking).. The fans are as predictable as a clock.. when I reach between 183 and 188, they engage.. that placement of the probe reacts (hysteresis) within 5*, meaning, if it comes on at 185*, it kicks off at 180*.. 183*, 178*.. ect... there is no lag with the probe in that location..

there is a ton of lag with the probe in the other locations.. it gets both a late start, and then has to work a lot more to cool (if it is on the hot side).. or, it kicks on too early and runs too short (if it is on the cool side)..

I slap that good ol' elm327 and fire up Torque on the phone, and can see I run a very consistent 185*, with the fans triggering for maybe ten second intervals with likely thirty seconds in between.. I'm pushing a little over 5kCFM.. I can adjust the controller to keep me around 180* steady if I like, or up to 190* if I like.. Relying on readings on either side of the engine creates a wider fluctuation.. likely 15*~20* or so..

do what makes you happy, and what you feel works.. I'm simply sharing where and why I get readings for the trigger event..