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post #2 of (permalink) Old Jul 17th, 2019, 4:07 am
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Join Date: Sep 2004
Location: Coventry, CT, USA
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Doesn't work that way with the ST4s (or any of the ST series I believe). Fan is turned on by the ECU. If you managed to change the temp sensor to one that somehow reads lower, not even sure you can in this case, you will effect what the ECU sees as engine temp which will also effect the fuel map. Not the way to go.

There are two sensors on the ST. One is for the digital temp readout on the dash. The other is for the ECU. No dedicated fan sensor like you'd find in the older Superbikes. Those actually have three different sensors on the same journal. ECU, Fan and a small thermistor for the temp gauge.

If you want control of the fan, you would need to add a manual switch that will apply a ground to the coil of the fan relay. The ECU controls relays and such by turning on a ground path for the voltage that is already sitting there. Splice in a manual ground and the fan relay will energize. Probably easier and less expensive than changing a temp sensor.

I have not made the modification, but there are many who have. I remember a few threads on the subject offering which relay and wire to splice in the ground.

Dan. "Painfully mistaking my big talk for the truth" Samantha Fish.
2003 ST4s (The Truck)
1995 916 (Junk Yard Dog)
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