Does you're car have a "dimmer switch" which affects the dimming of the hu? In all the cars i've had, the wire is just a constant voltage, with the amount of dimming set by the hu itself.Originally Posted by dfk70
Anyways, i've been messing around with a few ideas and the best I've come up with is essentially a small micro controller which has a light sensor attached to one input and the above mentioned wire attached to another. If the light sensor falls to a certain reading or the headlights are switched on for greater than a set period of time, the micro controller can send an output. Now, this output could be to a pin of a serial port on the PC or maybe directly interfacing to some modification of the screen. For ease, probably best if its to the pc and then this would need to be a plugin to sit between. Interestingly, the output doesn't necessarily have to be a binary "on/off", it could send an analogue signal to allow the amount of dimmming to be altered based on the actual ambient light.