Originally Posted by
smokeshow
PWM_Electric: 100-128Hz, capable of running with engine off, selectable DC ramp rates, RPM resonance-avoiding logic, only operates within a certain duty cycle band, ie 15-90% DC, utilizes open-circuit diagnostic for fault detection
PWM_EV: 2Hz (nominal), only commands fan DC after engine has been running for a calibratable amount of time, utilizes open-circuit diagnostic and sensed-RPM feedback diagnostic for fault detection
PWM_MRF: 20Hz (nominal), engine running only, utilizes open-circuit diagnostic and sensed-RPM feedback diagnostic for fault detection
Key distinction to make....this is a flexible control system. It can control a brushless Spal fan with an internal motor controller because the controller only pays attention to the signal. But the ECM will still fail the fan diagnostic if you have it set to EV or MRF without accessing and disabling diagnostics because the Spal motor controller has an internal 12V pull-up resistor, which the diagnostic sees as a short to power. For a brushless fan with an internal pullup, you might use a Schottky diode in line with the PWM signal to the fan. I haven't tried it yet, but that seems like a solid bet to isolate the 12V in the fan controller. Again, depends on what kind of fan you have....brushed fans will be different.