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Howdy! I'm currently in the process of replacing the roof panels on my '57 GMC and I figured while I have the roof open I would run the wires for the dome light and speaker right away instead of trying to fish them in later. My question is what is the correct wire gauge for these, the dome light and speaker, and are they one or two wires?

Thanks

AWG 14 will handle dome light with room to spare. Speaker uses two wires. Size of speaker wire is a loaded question as we don't know how big they are (wattage wise).

The dome light uses two wires as well, to an insulated socket without a ground which has a 2-contact bulb, also not grounded. Both wires go down the windshield A pillar and under the dash, one to ground at either a door switch or the dimmer switch of the dash light circuit at the headlight switch. The other lead to the dome light goes directly to the fuse block and is hot all the time. Use about a 5 amp fuse to that circuit.
Jerry

Jerry, Care to toss us the number of the bulb you wrote about above. A two post or contact bulb with the other side of the filament not grounded to bulb case is a different breed of cat. Thanks.

beltfed, it's not the bulb that's a breed apart, it's the socket, which is not grounded to the cab, so the bulb gets its ground from the "ground" wire back to the switch

Bill

12 volt GE, Wagner and others the number is 94 which is a two contact bulb for non-grounded sockets such as the dome light.

Thanks guys. I have no idea what size of speakers I'll end up putting in it, nothing too wild, but that is a long way off. That Tessco link that Tiny posted will help a bunch.

The light has not turned on here yet. Hotrod says it's an insulated socket with no ground at the socket. I get that part as the ground is provided by way of a door switch. If that ground wire is connected to the non grounded (at the light) socket via the door switch then I also get that. What I don't get, if the above is true, is what the other bulb contact is for.
I'm confused but that's nothing new.

2nd contact is power - ground no use without power

Bill

So the filament is between the two contacts and is not electrically tied to the socket. If so, then why do you care if the socket is grounded or not? It is electrically isolated from the two contacts, right?

the metal base of a bulb, which 'bayonets' into the socket, is one contact of the bulbs filament, the ground - the bottom button contact supplies power ... the isolated socket gets a ground away from the fixture, from a dedicated switch rather than from mounting to the body metal

Bill

I guess I misread what Jerry said about two contacts. I was thinking of a two filament bulb. Your explanation was well written. The fog is lifting. Thanks.

One more time- - - -dome light bulbs have two contacts on the base of the bulb. The filament is connected between them. Both of them are insulated from the brass bayonet sleeve that twists into the socket. Power is supplied to one base contact, and the wire connecting to the other contact is grounded by either the headlight switch shaft being turned to the "dome light" position, or by one of the door jamb switches. It's irrelevant whether or not the brass bulb sleeve or the socket is grounded- - - -neither end of the filament is connected to it.

OK- - - -found it! The 12 volt, double contact, single filament, insulated base dome light bulb is a #1004. There is a corresponding 6V bulb, but I haven't found a number for it yet. Stand by!

http://www.bellautomotive.com/Auto-Bulb-1004-p/22-5-01004-8.htm

Update #2- - - -6 volt equivalent, #8013:

http://www.bulbs.com/product/8013-6V

Jerry

Thanks Jerry. glad we clean that up.

The 1954 6v dome light is listed as Part # 453138 (No. 210)
The 12v equivalent is listed is listed as Part # 455136 (No. 1004)