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Discussion Starter #1 (Edited)
Hot wire high speed radiator fan switch

Has anyone wired in a switch to activate the high speed setting on the radiator fan?

I did a search but didn't see anything.
 

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The ECU controls of the radiator fan are pretty clever. It turns on the fans at low speed when the temperatures get to a certain point. If it gets to the second threshold, it changes them to the high speed setting. If the car exceeds 85 MPH (I think) it turns the fans off as the air flow through the radiator exceeds what the fans can do so there is no need for the fans to be powered.

If you need a bit of extra cooling, turn on your AC - that turns on the fans, and at least in my car, they stay on until I turn off the ignition, even after turning off the AC.

Other than that, why do you need to turn them on to high speed manually?
 

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Discussion Starter #6
I figured out how to hot wire the high speed on the radiator fans.

Not really hot wired. Relays are used to separate the fans from the ecu control when activated. No chance of short circuiting the ecu.

3 relays and some wire splicing. I had a buddy figure out the Lotus schematic.

I installed the relays this afternoon. Now I have high speed fan at the press of a button.

It's good for dyno days, track days and keeping the ac cooler.

Lotus wires the fans in series at low speed. High speed is parallel, the full 13.8v.
 
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