The dimmer function is controlled by pulse width modulation in my C5 Corvette and just happens to be inverted logic of what the N4 needs to see.

I used a npn transistor and three resistors to fix that.

Now the screen "reverses" or goes to a black background on the lowest dimmmer setting like it is supposed to.

This is not really covered in the documentation very well if at all.

I couldn't find any info so I just hung a scope on the dimmer lead and took a peek.

Here is a link on building one. Ignore the 5v and use 12v.

http://www.play-hookey.com/digital/expe ... erter.html

I used a third resistor (100k) as a pull down on the input.

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