we are good to go from here. the "X" on the back of the switch was put there for a different application than you have. although we have the basic functionallity you wanted, per your post above, the connections made by that "X" will prevent you from getting the LEDs to work correctly.
so with that, i will now tell you how to get the LEDs to work correctly.
disconnect the switch from all of the truck wiring.
now cut, unscrew, whatever the "X" from the back of the switch. there may be a convenient place to introduce a pair of side cutting pliers; or maybe you have to work at it for a bit. don't pry at the terminals themselves -- that might hose up the switch internals; just undo the "X" connections in the easiest way possible. you could just cut out a small section of the metallic conductor; then, if you ever wanted to reuse the switch for a different application, a small blob of solder will put the "X" back in place.
once the "X" is out of the picture, we are ready to reinsert the switch into the truck wiring:
here are the complete connections:
pin 1 = from headlight sensed +12V.
pin 2 = to relay.
pin 3 = constant power +12V.
pin 4 = no connection.
pin 5 = ground.
pin 6 = no connection.
this differs from the wiring i originally gave you a few posts back by only the addition of ground on pin 5.
now try the same tests as before. the LED should be on when the hellas are on, and only then.
the only slight issue that i can foresee is that the switch positions have a 50/50 chance of being "upside down" from what you want or what the markings on your switch may indicate. if that's the case, just reverse the connections to pins 1 and 3 and all will be fixed. it sounded like it may have worked out right the first time though.
good luck.
jim aka the wrooster
ps:
by the way, your original testing and documentation thereof made finding a solution much much much easier. most folks just write "it didn't work -- now what?", which is of course most unhelpful when trying to troubleshoot electrical or other similar problems. you went the extra mile and you should be applauded for this. good job.