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Discussion summary
YOUR RESEARCHDual radiator fan hack switch question!
Leading reported evidence
Replace resistors behind the radiator fans
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Performed · outcome unconfirmed · Original poster
And yes, before anyone says it I have replaced both resistors behind the radiator fans.
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Performed · outcome unconfirmed
That is why relays are used with the small switches in the dash.
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Suggestion · Original poster
I only got this switch because I have blank ones in my dash and figured this would be a clean install.
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Suggestion
If you are using the switch to run both fans manually, you need a switch that can handle the start and running amps of the motors.
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Suggestion · Original poster
And yes I just want the switch to run both fans manually.
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I've done all that and I'm still getting 210F coolant temps, which is fine..
Quick question about this switch.. I was reading about different kinds of switches tonight because I wanted to be prepared to do the dual fan hack tomorrow and came across this..
"All the switches on the center of the dash (i.e. PSM, Defroster, Heated Seats) and referred to as TIP switches. They are not on/off switches but rather work through relays."
So, does this mean my switch will not work? If not, what else can I use? Hopefully something that's already on the car.. Kind of in a rush since autocross is this Sunday. Car is a 2002 C2 911.
Thanks!
If you are using the switch to run both fans manually, you need a switch that can handle the start and running amps of the motors. That is why relays are used with the small switches in the dash. It only takes a small amount of current to actuate the relay to close the contacts in the relay. The contacts and metal conductors in the relay are large enough to handle the current. You can do the same thing, but it will take a bit of research to figure out what components you need and how to wire it up.
I should add that relays are often used when installing "upgraded" aftermarket headlights. There are probably some applicable YouTube videos.
I ran my car at Road Atlanta, once in July and once this month (August) with the stock cooling system. I had no issues. I did remove the front bumper prior to the first track day and cleaned out the leaves and other crud off the radiators.
Hmmm, should I just go to the store and purchase a generic toggle switch then? And yes I just want the switch to run both fans manually. I only got this switch because I have blank ones in my dash and figured this would be a clean install.
I've done all that and I'm still getting 210F coolant temps, which is fine.. but I don't like that. Especially waiting in the grid during autocross events. A manual fan toggle switch is just what I want.
And yes, before anyone says it I have replaced both resistors behind the radiator fans.
This doesn't help cooling much, if at all. A thermostat is there to allow the engine to get up to operating temperature quickly, then it opens to allow cooling. A lower temp thermostat simply opens at a lower temperature, which means you are not letting the engine warm up completely. The cooling capacity doesn't change in either scenario.
It is a good idea to let the fans run in hot conditions.
Especially when standing still without driving wind cooling the rads. Also taking into account that at idle rpms the pump rotates considerably slower then under driving so little water gets moved around, makes the thermostat less responsive to open more when coming from driving to a stand still adding further to the problem of enough cooling capacity.
You could use this to trigger the fans to come on in high speed mode. As such you will automatically provide some extra cooling when BEFORE it gets to hot in the engine.
I have an extra temp sensor which monitors the coolant temp exiting the rads. It was a part of the cooling modification package offered by my Indy. If this temperature comes above a certain treshhold it triggers the fans to run at high speed providing the necessary airflow in order to control the cooling water temperature entering the engine and before temperatures rise too high.
No idea how in my case the trigger is established. Difficult to say if the DME could be reprogrammed with an extra temperature input. Or that the sensor input which controls the fan speeds gets fooled by a tweaked signal coming from the rads rather than the engine temperature.
