PWM cooling fan(s) control using ECM

[mikels]

Originally Posted by parsonsj

Yes, it would be awesome for such a standalone controller to also support an AC pressure sensor. All the fan controllers I've seen just turn on the fans to a set speed (usually 100%) with a 12V input signal when the AC is turned on.

This functionality is built into OEM control logic (E40, E38, E67, etc. with PWM fan control. There are cal's based on following:

• ECT
• Oil temp
• Trans temp
• IAT
• AC pressure

Way logic works is a % output based on each of these inputs - and highest request wins. In other words, if ECT is requesting 30%, but AC pressure is requesting 42%, fans are driven @ 42%.

Stand-alone controller would need provisions for a scaled 0-5V input based on AC pressure with a cal relating that pressure to a requested output. And same logic where highest request wins.

Dave