Megasquirt Support Forum (MSEXTRA)

i would like to see if we could get pwm fan support. granted this can be done easily with a generic pwm output but that leaves no method to turn on the fan with ac.

I'd like this feature as well, but perhaps in a slightly more generic way that would allow turning on/table/off any of the generic PWM outputs based on another input/function.

x3, this is keeping me from running a pwm'd fan.

This can be done easily with a arduino, what makes dificult to me is how do you control a hi power fan.. Using a relay with pwm it will kill it in no time, right?

filipesbp wrote:This can be done easily with a arduino, what makes dificult to me is how do you control a hi power fan.. Using a relay with pwm it will kill it in no time, right?

High current solid state relays exist and will take PWM, Ford FPDM modules, OEM fan controllers, etc. I have controlled a fan via PWM using an Arduino and a Ford FPDM before.

I imagine this should be easy to integrate into the MS3 since it already has all of the necessary inputs and outputs. It will do generic PWM, Fuel Pump PWM, Alternator control, etc. Having this feature integrate with the A/C and ECT would be very handy!!!

filipesbp wrote:This can be done easily with a arduino, what makes dificult to me is how do you control a hi power fan.. Using a relay with pwm it will kill it in no time, right?

I'm using a module built for PWM fan control out of a Chrysler Minivan (Dorman 902-310 is the partnumber I used). The module was about $25 with a connector pigtail.

theturbodog wrote:

filipesbp wrote:This can be done easily with a arduino, what makes dificult to me is how do you control a hi power fan.. Using a relay with pwm it will kill it in no time, right?

I'm using a module built for PWM fan control out of a Chrysler Minivan (Dorman 902-310 is the partnumber I used). The module was about $25 with a connector pigtail.

Hi, the Dorman looks like a good option, would you mind sharing wiring details and tuner studio settings please?


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http://photobucket.com/gallery/user/Tyl ... MTQ=/?ref= Is a nice picture of the wiring leads.

The connector pigtail has 4 leads, 2 about 12ga and 2 roughly 20 gauge.
1: Fused Power : Green(large)
2: Fan+ : Green(large)
3: Ground : Purple(thin)
4: PWM Signal : Purple(thin)

30-100% duty cycle is what the module will take. I run mine at 19.5Hz because of timer sharing(I'm sharing frequency with boost control), but if I recall I ran it at several other frequencies when I was messing with boost, idle, and VVT outputs to get a group of frequencies that worked for all my stuff. The only quirk really is that you have to set the lowest fan on temperature to 0.1 degrees below the 2nd bin to get a crisp 0% -30% duty switch otherwise you end up interpolating from 0 to 30 and that drives the unit below the 30% duty spec(I don't know if it would hurt it if you did, but I'm trying to drive it how the factory does).

I'm running it off of Generic PWM A with water temp to drive my table. I'm also using engine RPM as a proxy for vehicle speed since you can't yet control both axes(ideally would use VSS vs CLT). So at low rpm I assume probably lower speed so add in a little more fan, higher rpm probably means more speed so i dial back the fan at any given temp.

theturbodog wrote:http://photobucket.com/gallery/user/Tyl ... MTQ=/?ref= Is a nice picture of the wiring leads.

The connector pigtail has 4 leads, 2 about 12ga and 2 roughly 20 gauge.
1: Fused Power : Green(large)
2: Fan+ : Green(large)
3: Ground : Purple(thin)
4: PWM Signal : Purple(thin)

30-100% duty cycle is what the module will take. I run mine at 19.5Hz because of timer sharing(I'm sharing frequency with boost control), but if I recall I ran it at several other frequencies when I was messing with boost, idle, and VVT outputs to get a group of frequencies that worked for all my stuff. The only quirk really is that you have to set the lowest fan on temperature to 0.1 degrees below the 2nd bin to get a crisp 0% -30% duty switch otherwise you end up interpolating from 0 to 30 and that drives the unit below the 30% duty spec(I don't know if it would hurt it if you did, but I'm trying to drive it how the factory does).

I'm running it off of Generic PWM A with water temp to drive my table. I'm also using engine RPM as a proxy for vehicle speed since you can't yet control both axes(ideally would use VSS vs CLT). So at low rpm I assume probably lower speed so add in a little more fan, higher rpm probably means more speed so i dial back the fan at any given temp.

Thank you for the great reply!!


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With a few small changes to what has been suggested, this function can also be used for electric water pumps.

The only really trick with water pump control is that you always need it running a very low speed or pulse the pump in order to avoid localized boiling.