I have an aftermarket ECU (Holley Terminator X) that has PWM(-) outputs. I believe this means the output is pulsed between an open state and a ground at the programmed frequency. I am looking to buy some brushless radiator fans that need a pwm 12v signal to control speed. In other words 12v 100% duty cycle is full speed, 0 duty cycle or no 12v is off, a 12v square wave at 50% duty cycle will run the fan half speed, fan speed will increase with duty cycle. Is there a simple circuit I could build to change the PWM ground signal to a PWM high or voltage signal so the ECU can control the fan speed. It would be much simpler in my mind to let the ECU control the fans rather than having to add the fan companies PWM temp controller with its own temp sensors and wiring. I'm an auto tech and have a decent understanding of electronics, but not enough to design a circuit from scratch, or what type of circuit to google here.