When I pulled the headlight switch all the way out last night my lights would not open, and did not illuminate. No pop-up, no light. Parking and brake lights operate.

Best way to test the headlight switch? I'd like know how to test the wiring "downstream of the switch too. What circuits are closed when the headlight switch is pulled all the way out? Asking 'cause I was also seeing an intermittent alternator light that makes me think "voltage drop" at some connection and because I don't fully understand how the headlight switch acts on all the relays.

As I understand it, the relays at the bucket assemblies activate their respective motors and the high-low relay responds to input from the switch in the steering column. Since the lights pop-up and illuminate when the switch is pulled, the dash switch must directly energize a pin on all three relays?

.....Grounding is very important!

try this

http://members.rennlist.com/pbanders/headl...h_internals.htm

One of the wires to Fuse (1) is from the "downstream" leg of the high-beam indictor light on the tach. (Power to the indicator light is unfused. I assume it must pigtail off of the high beam lead from the high/low beam relay) Whatever the problem is with the headlights is making high-beam indicator light up when the parking lights are on.

Fuse 1 serves, or "goes to," the left high-beam. If the high-beam circuit can't close, perhaps the current at "the top" of fuse 1 reverses polarity and finds ground through the light. Does this help me isolate the problem? I can't figure out the rest of the diagram well enough to know.

thanks, 76-914, now I'll know how to fix the switch if that's the problem.

OMT, no fog lights/relay on this car.

I expect that you have already assured that you did not knock the fuse out with your knee, and that the fuses are in fact all good? sorry to ask - just making sure! td

Good call tadink. I had, in fact, knocked 10, 11, 12 out with my foot earlier that day and 12 may be the HL motors. but they've been checked, terminals cleaned and replaced.
I went through all the fuses and they're seated and clean. I would like to know whether there is a single fuse that would knock out the whole headlight system. My interpretation of the wire diagram is no, but I'm not very good at reading it.

How your headlights work....

Thank you so much, that was exactly what I was searching for. Great article too -- well done! Everyone should check it out.

BTW, my prob. was the switch, of course.