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Adjustable speed fan override DIY under $10 only 2 parts

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Adjustable speed fan override DIY under $10 only 2 parts

Old 10-10-2018, 04:53 PM
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DblTrbl
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Default Adjustable speed fan override DIY under $10 only 2 parts

The C6 fan controller is controlled by a low power PWM signal wire from the ECM.
Here is all you need to have a variable speed override:



The gizmo on the right is a $5 PWM generator from EBAY. https://www.ebay.com/itm/1Hz-150KHz-PWM-Pulse-Frequency-Duty-Cycle-Adjustable-Module-Signal-Generator/123362300644?epid=14012860094&hash=item1 cb8f752e4:gsQAAOSwMudblh4p:rk:13:pf:0

The switch on the left is any dual pole switch.

As DIY projects go, the wiring is extremely simple.

I am not in business. I am not selling anything. I'm also not responsible if you or I make any mistaeks.
I have tested this combo with a C6 style fan controller module on my bench. I don't have a C6 to test this in.

The switch completely disconnects the PWM generator from the car so when the switch is on, the PWM generator controls the fan. When it's off, the ECM controls the fan as normal .

I'll draw up a wiring diagram soon.

Last edited by DblTrbl; 10-11-2018 at 12:47 PM.
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Old 10-11-2018, 06:03 AM
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Sub'd
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Old 10-11-2018, 12:14 PM
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Here's a wiring diagram. I modified a C6 Z06 diagram I found.

The circuit is all low power, in the several milliamps range, so all the wires can be signal wires.
The SPD CTRL wire between the ECM and the Fan Control Module needs to be cut (anywhere along the length) and connected to the switch. Make sure you connect the side going to the Fan Control Module to the center pole of the switch.
If you connect the 12Volts to an Ignition 12 volt source, the override only works with the ignition on. If you connect it to the battery, the override should work even when the car is off, so it's up to you to remember to turn the override off once it all cooled off, or risk a dead battery.

The switch doesn't have to be big and ugly like in the picture. Any small Dual Pole Dual Throw (DPDT) switch can be used.

Basically, the switch is changing the source of the PWM signal that the Fan Module sees from one PWM source to the other. It also turns the power on to the module so will know when the override is in control.
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Old 10-11-2018, 12:18 PM
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Ignore the Power Input - (V- in the picture) connector.
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Old 10-11-2018, 01:49 PM
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This is pretty cool. Could you post up a video of the whole setup functioning?
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Old 10-11-2018, 05:29 PM
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I could post a video of the setup working in my Turbocharged 6.0 C3. Is that going to help?
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Old 10-12-2018, 01:03 AM
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Here's a video of the fan module connected to the dual radiator fans in my Turbo C3 Vette.


The C6 module does not have continuously variable speeds. Instead, it has a good number of speed increments it steps through.
Maximum speed is at roughly 10% duty cycle. Minimum speed is at 90%. 0% and 100% PWM will both turn the fans off.

The PWM frequency is set to 128 hz in the video, but actually, the fan module isn't particular about the frequency. I've tested it between 50HZ and 5000hz and it pretty much behaves the same way across the board.

The PWM generator remembers the last setting even when the power is off, so if you set a speed (PWM), it will go to that speed next time the unit is turned on.
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Old 10-14-2018, 09:43 PM
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Thanks, man. I can think of quite a few projects that those things might come in handy.
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Old 10-15-2018, 10:26 AM
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Originally Posted by 69427 View Post
Thanks, man. I can think of quite a few projects that those things might come in handy.
YW.

If you need a pre-set high and low speed override setup, you would need another PWM generator module and another switch. One switch would be override or ECM and another would be high or low. Then you could pre-set what the high and low fan speeds should be and not fiddle with the buttons after that. I can draw up the wiring for that setup if someone wants it.

Last edited by DblTrbl; 10-15-2018 at 10:26 AM.
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