I am going to put a aftermarket rear view mirror in my XK8. The YU wire goes low to turn on the headlights. I have a wire lume from the mirror and I am looking for a photodiode to mount in the lume to control the auto headlights. Has anyone done this and what was the part number from digikey or others that was used?

CJ, you have a red car so less problematic than my Titanium (read asphalt grey) XK8, but still - maybe you want to leave the auto on constantly tripped creating DRL with your low beams? (DRL daytime running lights) I did so by placing a piece of tape over the sensor = lights on when auto is on and ignition is on.

Benefit, you're a lot easier to see. Only drawback is dashboard lights dim slightly. Avoiding an accident is well worth that IMO.

John

Didn't answer your question. A photo diode is just a switch that allows current to flow in 1 direction when it senses light (so it is always polarized can only be correctly wired in 1 way). As I recall this is just a trip circuit so no significant current involved . Find any one that's rated at 12volts you'll be good. Choose it based on size and shape from there.

John

Have you actually tested that YU wire to confirm that is what it does?

You might want to dismantle the original mirror and use whatever circuitry there is in that, before trying to re invent the wheel. As a general caution I would never connect up random components to the car's wiring unless I knew exactly what I was replacing.

Dibbit good point, why not just reuse the original diode?

Just be careful of the goop inside the original mirror. I'd do it out side, newspapers and rubber gloves...

J

That interior mirror "goop" is best described as "dragon's blood". Highly toxic to anything it comes in contact with....

From memory it's a Light Dependent Resistor which will quite possibly have a circuit board to go with it inside the mirror - apart from anything else there is a knob to adjust the cut off point, so it might be more complicated than just connecting one component to the control wire.

Yes I agree Dibbit, I forgot about that potentiometer for the trip circuit. Its gonna complicate customizations a bit. Maybe that always on DRL is sounding better CJ?

John

For DRL I just ran a wire to ground on the fog lights relay pin 2. I have switched dim, highs and fog's to fanless LED. It isn't a big deal to just turn on the headlights. Does the YU wire go high at night or low to trigger?

https://www.jaguarforums.com/forum/x...highlight=Auto

Looks like grounding the yellow blue wire = headlight on.

John

Thanks.