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Manual Radiator Fan Switches

 
Old 12-29-2017, 10:01 AM
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Blue Chip
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Default Manual Radiator Fan Switches

As my car continues its journey from street car, to mixed use, to mainly track, to nearly all track - I am considering putting a manual override for the radiator and engine compartment fans (or even getting rid of the temp sensors all together and wiring them into a 3 way switch mounted to a panel where the radio used to be... OFF, LOW, HI.

Anyone have any thoughts on this (or experience)?
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Old 12-29-2017, 10:46 AM
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Good idea. I did the same on my last race car.
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Old 12-29-2017, 10:49 AM
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Old 12-29-2017, 11:48 AM
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I saw this - I'm not 100% clear on the instructions - but it doesn't seem that hard. Temp management (especially in Florida in the summer) is critical. The override seems like a good idea.
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Old 12-29-2017, 12:21 PM
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I think what the fan hack taps into is the Relays. You might have to play around with those, but I think it entails tapping into the back of the relay, locating the ground wire, routing it your three way switch and grounding it so the fans turn on. Grounding 19 and 21 will turn on the fans low. Grounding 20 and 22 will turn on the fans high.


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Old 01-09-2018, 12:42 PM
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That's what I am wondering - how do I tap into the back of the relay and which pins?

Edit - it actually sounds SUPER easy if that's all it is.

Basically tap into the ground for each of the relays (20 and 22) run it to a switch - then to a grounding point on the car... all you're doing at that point is a ground jump. When I get the car back from it's transplant I will give it a go.
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Old 07-12-2019, 07:53 PM
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Guys, have a question on this. I just did this mod to my cars tapping into connection 85 on relay 20 and 22 passing it thru a switch to ground, and it works correctly, but when I turn the key off the fan continue to run.

The fans actually run on high speed any time I hit that switch even with the key out of the car and the doors locked. I thought they would only run with the ignition on. Any ideas??
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Old 07-13-2019, 08:23 PM
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Been a regular at the road race track for a long time,, I'd never go to 100% manual control,
because you WILL forget to flip the switch and heat the motor up eventually.
If your going to wire a switch wire it so there is a sensor that can still turn the fan on, just
raise the temp sensor to a higher number so if the motor gets hot
when you have the fans locked out the sensor will over-ride prevent total meltdown.
Basically your wiring it for off-auto/normal-auto/Lock ON

I have lost count of the number of cars I've watched boil engines over in the hot pits or
while waiting to scale after an event. Or waiting to run their autocross run.. When they forgot
to turn the fans back on.
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Old 07-13-2019, 08:51 PM
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Yes understand, I am not wiring for 100% manual. The factory fan control system is still in place and working. This is a fan high speed overwrite where I can force the fan high speed to on via a switch.
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Old 07-14-2019, 01:53 AM
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Just another thought,, When I set this up for different folks, I wired it so it would turn the
emergency flashers on on so track day guys didn't leave it on and then run their battery down.
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Old 07-14-2019, 08:17 PM
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I wired in an led light, picking the ground from the switch and the positive from an ignition switches fuse, but get this.
The led works as expected when the ignition is on or for some time after I turn the car off, it lights up when the fans run. But when the car goes into a dormant state after it has been off for a while, the led lights up no matter what position the switch is on, of course the fans donĺt run.
The Germans do something weird with ground when the car goes into sleep mode. Any ideas??
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