PWM cooling fan(s) control using ECM

[andrewb70]

The information below is for a Holley HP or Dominator system, but I thought it would be handy to post it here.


So recently a buddy of mine presented me with a challenge. He has a street car that uses a Dominator ECU and he is using the C6 fan controller, just like I am. However, his car has A/C and he wanted to have the fan turn on at a predefined duty cycle whenever the A/C kicks on. I also know that some of you have the desire to be able to toggle the fan to full speed while at the track, and with the configuration that I previously posted, this is not possible. There may be other ways to do this, but this is what I came up with and it seems to work very well. I am testing it with a manual trigger through a virtual switch on my Holley 7" dash, but any switch will work, including a A/C compressor trigger.

First you need to create an Input and assign it to a pin (hopefully y'all know how to do that already). In my case I created a 20v sensor, but I see no reason why creating a 5v sensor wouldn't work either...



Then you have to configure the sensor. I chose the Custom 20v from the dropdown menu and gave the sensor a minimum value of 0 and a max of 1. Essentially what I am doing is creating a binary switch. The reason for doing this is that simple 12+ or Ground triggers are not selectable in the PWM table, but custom sensors are!



Here is the bottom of the screen...On the bottom scale, half the values are given a value of zero and the rest ramps up from 10-20v. Then I configure voltage values of zero to be zero and voltage values above 10v to have a value of 1.




Now we can move to the PWM output screen and configure it. The Y-axis remains CTS but instead of having MPH on the X-axis, as I used to have, now I select the new A/C sensor that I created. The resulting table looks like this:




This essentially splits the PWM table into to different conditions and they function independently, based on whether the trigger we created is ON (value 1) or OFF (value 0)...This set-up should work just fine for anyone that wants to turn their fan on at the drag strip...but it creates a different situation if you want the fan on when the A/C is on. With this configuration, even at highway speeds, the fan will be running at 50% (or whatever we assign to the cell of value 1 on the X-axis), which isn't really needed or desirable. In order to fix this, I have created conditional sensor triggers that will activate the PWM table.



I have set MPH as a trigger and set it to activate the table at speeds below 30 mph, and I also set the table to activate when temperatures are above 200 degrees. So in my friends case, with the A/C ON the fan will operate at 50% while at speeds below 30mph. Above that speed the fan is OFF, even when the A/C ON, however, if the CTS goes above 200 degrees, the table PWM table is activated again. Also keep in mind that the whole left side of the PWM table can have different values in all the cells. So you can have a minimum of 50%, but if CTS starts climbing, higher fan speeds can be commended.

With the A/C OFF, again, the right side of the PWM table is activated below 30 mph (this of course can be changed) or when the CTS goes above 200 degrees (this too can be changed).

This configuration should work for different set-ups and scenarios but the trigger values will have to be tuned to your particular combinations. This is due to variance in fans, hoods, thermostats, etc....

Any and all comments are welcome...

Andrew

[mikentosh]

Originally Posted by andrewb70

The information below is for a Holley HP or Dominator system, but I thought it would be handy to post it here.

Andrew, great information! I was a little stumped on how to get the A/C to trigger the PWM fans, so will try this now. Thanks!

[Larry R]

Originally Posted by andrewb70

The information below is for a Holley HP or Dominator system, but I thought it would be handy to post it here.


So recently a buddy of mine presented me with a challenge. He has a street car that uses a Dominator ECU and he is using the C6 fan controller, just like I am. However, his car has A/C and he wanted to have the fan turn on at a predefined duty cycle whenever the A/C kicks on. I also know that some of you have the desire to be able to toggle the fan to full speed while at the track, and with the configuration that I previously posted, this is not possible. There may be other ways to do this, but this is what I came up with and it seems to work very well. I am testing it with a manual trigger through a virtual switch on my Holley 7" dash, but any switch will work, including a A/C compressor trigger.

First you need to create an Input and assign it to a pin (hopefully y'all know how to do that already). In my case I created a 20v sensor, but I see no reason why creating a 5v sensor wouldn't work either...



Then you have to configure the sensor. I chose the Custom 20v from the dropdown menu and gave the sensor a minimum value of 0 and a max of 1. Essentially what I am doing is creating a binary switch. The reason for doing this is that simple 12+ or Ground triggers are not selectable in the PWM table, but custom sensors are!



Here is the bottom of the screen...On the bottom scale, half the values are given a value of zero and the rest ramps up from 10-20v. Then I configure voltage values of zero to be zero and voltage values above 10v to have a value of 1.




Now we can move to the PWM output screen and configure it. The Y-axis remains CTS but instead of having MPH on the X-axis, as I used to have, now I select the new A/C sensor that I created. The resulting table looks like this:




This essentially splits the PWM table into to different conditions and they function independently, based on whether the trigger we created is ON (value 1) or OFF (value 0)...This set-up should work just fine for anyone that wants to turn their fan on at the drag strip...but it creates a different situation if you want the fan on when the A/C is on. With this configuration, even at highway speeds, the fan will be running at 50% (or whatever we assign to the cell of value 1 on the X-axis), which isn't really needed or desirable. In order to fix this, I have created conditional sensor triggers that will activate the PWM table.



I have set MPH as a trigger and set it to activate the table at speeds below 30 mph, and I also set the table to activate when temperatures are above 200 degrees. So in my friends case, with the A/C ON the fan will operate at 50% while at speeds below 30mph. Above that speed the fan is OFF, even when the A/C ON, however, if the CTS goes above 200 degrees, the table PWM table is activated again. Also keep in mind that the whole left side of the PWM table can have different values in all the cells. So you can have a minimum of 50%, but if CTS starts climbing, higher fan speeds can be commended.

With the A/C OFF, again, the right side of the PWM table is activated below 30 mph (this of course can be changed) or when the CTS goes above 200 degrees (this too can be changed).

This configuration should work for different set-ups and scenarios but the trigger values will have to be tuned to your particular combinations. This is due to variance in fans, hoods, thermostats, etc....

Any and all comments are welcome...

Andrew

I am trying to replicate or at least to use what you created here for my car. I cannot get the LH column on the calibration table to accept the number 1 as you have in your post. Also you will note it says "A/C (x10)" but I did not put that in so I do not know where that came from. Any help you can offer will be appreciated. Larry

[andrewb70]

The input needs to be "custom 20v" not custom 5v.

Andrew

[andrewb70]

You actually don't have to do any of this if you have a linear AC pressure sensor. You can just create a AC pressure input and use it and coolant temp as your two axes of the PWM table. You can also add logic to turn the fan off above a certain speed and turn the fans on again if AC pressure or coolant temp rise, regardless of how fast you're moving.

What I showed is better suited for a system where there is no pressure sensor in the AC, but there is an input to the ECU to let it know that the compressor is ON.

Andrew

[Larry R]

Ok, Thanks. I assumed since I am using a linear pressure sensor that is 5 volts that I needed to have the value at 5 volts; I will set it at 20 volts. I would like to have my dual Spal fans run through the PWM, (I have the Ford version PWM), but be able to have the fan run a little faster when the A/C pressure rises to values near to what a trinary switch does.

This forum has been very enlightening for me, thanks to you and others. Larry