how to read a 12V PWM signal
Discussion
I'm trying to diagnose a cooling fan fault on a 1999 BMW E46 328i. The electric cooling fan doesn't kick in and the car overheats. There is a constant 12V at the fan. The fan is controlled by a PWM signal through a third wire. I would like to try to read the signal on that wire to see if the fan is getting any sort of signal or if it's the controller on the fan itself. I understand it's a PWM signal but not sure if it's 12V or perhaps 3 or 5V. Any ideas how I can read the signal? Some sort of USB oscilloscope adapter for a laptop?
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