Quote:
Originally Posted by Billybob
I'm going to presume you have not looked at the control signal from the CCU to the controller/porcupine with any type of oscilloscope?
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I actually looked at the signal yesterday with an oscilloscope while diagnosing another member's fan problems.
The signal coming from the CCU ('86 and upward models only) is NOT a PWM signal, but a DC voltage. There are 6 fan speeds that I know of, low = 1, auto = 2-5, high = 6.
The voltages I measured were:
Off = 0v
1 = 1.2v
2 = 2.0v
6 = 7.0v
I did not measure fan speeds 3, 4, and 5.
When I get my clamp-on current meter back, I will be able to measure the current on the control signal. My guess is that it is very low. It is probably going to a high impedance input.
To do what you want, a simple 7v regulator connected to a single turn pot should suffice. Maybe a 5k ohm pot. Connect the regulator to the full CW terminal and ground to the other end. The center tap goes to the fan controller.
The 5k pot is just a guess. I'll know more when I know how many milliamps the factory circuit draws.