GM sunroof automation - success/beware

Sorry about the delay... holiday weekend and all. I chose an optoisolator on my uncle's recommendation. It was the only thing he could think of that would be able to "read" such a low-current reference voltage of the limit switches. The Zener diode is used to drop the 12V input down a little so when the roof is closed (i.e. limit switch changes to +5V) the difference in potential would be small enough not to light the internal LED of the 4N33... which is what I wanted.