VERY basic electrical question - need help ASAP

[767Jockey]

Guys,
I'm an electrical zero. I'm re-wiring my car and have a simple question. Ron Francis, who I got my harness from, is closed today so I figured I'd try you guys. The harness instructions tell me to run two wires to each tail light housing. One goes to the "dim" filament in the bulb, and one goes to the "bright" filament. Both leads are black on the tail lights, they appear to be identical. Each tail light housing has only one bulb, it's a #1157 bulb with two contacts. Both contacts look identical. If it matters, they're the standard Lucas L542 tail light housings.

My question is, how in the world do I tell which is the "dim" filament and which is the "bright" filament? The only difference that I can see in the housing is that one bayonet pin in the bulb socket appears higher than the other. Everything else appears identical. Help, anyone? I'm thoroughly confuzzled.....

[Three Peaks]

Take a couple wires, hook one to the ground of a 12V battery and one to the hot. Strip the other ends and leave the ground touching the outer shellholder of the Tailight. Try both wires on the tailight with the hot wire to see which one is the bright filament.


Bob

[mr0077]

I'm not sure if there's a more elegant answer, but the "bright" lead feeds the brake filament, and the "dim" lead feeds the tail light filament in the bulb. Put a bulb in the socket (it will only go in one way), ground the case and put 12V B+ to each pigtail and mark the one that is the brighter of the two.
There's probably a better way to tell on sight, but the above will work.
Good luck

[767Jockey]

I thought of that, but I'll fall on my sword here and ask a really dumb question. To the naked eye in daylight, is one really visibly dimmer than the other? Has anyone actually done this? I'd hate to get it wrong, after the darn brake lines, this is my second least favorite job on this car.

[Maurice Johnson]

767'

The socket has staggered pin slots. The bulb will go in the right way, and the illumination will be correct for stop and tail lite. Provided you have the feeds correct , that is.

[jwoodard]

To answer your question 767, yes, you should be able to detect a difference in the illumination.

[mr0077]

And then, there is the possibility of putting the bulb in some sort of shade (maybe use a tube over the bulb or tail light?)! I agree with Jim, you should be able to tell, even in daylight. Intensity difference will be somewhat similar to your daily driver's brake v. tail lights.

[patrickt]

767Jockey, hook them up without regard to correctness. Then have someone turn the lights on and press the brakes. If the lights look identical on both sides, switch the wires on one. Then hit the brakes again with the lights on and decide which side looks better. Then switch the wires on the opposite side. Voila.

[767Jockey]

I've got it finally, cancel the self induced emergency. The answer is you can definitely see the difference in the daylight. Thanks, guys, I've got it straightened out now.