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:
https://cimg9.ibsrv.net/gimg/www.cor...8c1db52d88.jpg


The gizmo on the right is a $5 PWM generator from EBAY. https://www.ebay.com/itm/1Hz-150KHz-...h4p: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.

Here's a wiring diagram. I modified a C6 Z06 diagram I found.
https://cimg1.ibsrv.net/gimg/www.cor...3c91fc1e49.jpg
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.

https://cimg2.ibsrv.net/gimg/www.cor...1ad683be0c.jpg
Ignore the Power Input - (V- in the picture) connector.

This is pretty cool. Could you post up a video of the whole setup functioning?

I could post a video of the setup working in my Turbocharged 6.0 C3. Is that going to help?

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.

Thanks, man. I can think of quite a few projects that those things might come in handy. :thumbs:

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.

I'm surprised none of the C6 racers have jumped on this offer. I guess someone out there must have an easier way.

This is really cool. I've been thinking about doing the same thing, only using the PWM generator that has the knob for adjustment. $5 from China.

cheaper and easier??
 

Thanks for the info Dbl Tbrl, but looking at the wiring diagram ,I think there could be an easier and cheaper way to do this. Let me try to explain....Instead of using an additional PWM, why not use the existing one? Here's how it would work; The DPDT Sw. is cut into the ECT sensor, which is a resistor that varies with temperature. A DPDT will be wiring to the ECT sensor circuit instead of PWM wire. When manual operation is desired, just flip the DPDT Sw. to remove the ECT Sensor from the circuit, then a potentiometer (Pot.)(variable resistor) wired to the other side of the DPDT Sw. will vary the resistance, the change in resistance will translate to a change in fan speed through the existing PWM.
No extra PWM needed, just a potentiometer. The correct range of resistance for the Pot. will have to be determined based on the resistance range of the ECT Sensor. I believe this will work, can any elec. gurus confirm this?? I will have to throw up a diagram for clarity.

Does sound easy. Any alarms generated or safe mode operations by this?

Don't know , I just thought of it. Give it a try