Temperature control of thermo fans.

[OnAll-FOUR]

I was wondering if anybody has some info or done the measurements of using the coolant temp from the cool or hot of the radiator to switch the thermo fans in/out?

I have a wolf v500 installed in my St185 and was thinking of wiring thermo control to the ECU rather than the stock temperature switch.

Is this worth doing? After reading the termo fan FAQ there was a small amount of discussion about using the hot temperatures or or the cold temperatures to switch the fans in and out, but no real conclusions.

The stock St185 temp switch operates around 92-83 Deg C I believe on the cool side of the radiator. So I assume the idea of this is to regulate the water temperature going into the block is this the best way?

Where if I use the ECUs temp, this is on the 3SGTEs water neck on the hot side. I regularly see temps in excess of 100deg C when driving from this point (Calibrated with a IR temp sensor +/- 2 Deg C ). If I was to use the ECU to control the Thermos what hot side temperature should I use to cut the fan in and out?

I wasn't sure if I should clog up the Termo FAQ with this Q as that seemed to be more about the wiring.

[Guyana00]

The first range seems a bit low to me. I would say to go with the ECU's temp

[thechuckster]

it's normal: factory thermofan sensor is in cool side (bottom) of radiator

[OnAll-FOUR]

Thanks for the input guys. Is this such a noob question or is it something people are not sure about?

Surely some people with aftermarket ECUs have them controlling the thermos? or do they just leave it with the factory setup?

[CrUZida]

Its more the fact that very few people have ever measured the temps.

Anyone with a RWD (which from factory usually doesn't have a thermo) who goes aftermarket and puts on a thermo fan pretty much always has the ecu controlling it.


I've always set my thermo's to come on ~12-15degC above the thermostat opening temperature.