Gauge of wire? Dome light troubleshooting; 1967 12-volt

[DadaCheese]

I'll admit; I did NOT go through all of the many, many results and threads I found by searching.

QUESTIONS BELOW.

Need to troubleshoot and fix my rear ceiling dome light.

Here's my plan of action:

--Check Fuses (done; they're fine)
--Look at basic connection(s) within the rear dome light (looks fine)
--Test Dome light's Light Bulbs (done; they're fine).
--Test all combinations of dome light switch in conjunction with the the front steering column DOME LIGHT SWITCH (done; not fine; no combination works.).
__________(below is where I am at/planning on doing)__________
--Test/replace/look at connections to the front cab DOME LIGHT SWITCH (WW Part # 211947511C).
--Test/replace the dome light fixture (WW repro. Part #211947107A)
--IF the problem is isolated to be the wire that goes to the dome light, try to replace that wire without removing wood ceiling panels. (Possible?)


SO; quick questions:

1) Replacing the wire for the back dome light in my 1967 Westfalia; what gauge?
2) Best source for buying (more than enough) of said wire? Got a link for me?
3) IS it possible to replace that wire without removing my wood Westfalia ceiling panels?
4) Does anyone know the exact, and full, path of that wire (from the factory) so that I have a mental visual when/if pulling a new wire through (without removing wood headliner)?

...I have a very thin flat steel pull line/fish tape; I am hoping I don't have to replace that wire, but if I do, will that work?

Thanks in advance, everyone!
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Dada as in dadaism.
Cheese as in the stuff I love to eat.

[Jeler]

[DadaCheese]

[johny__utah]

x2 on a bad ground. remove & clean the dome light, inspect the on-off switch to make sure it is making proper contact. little sandpaper around the mounting screw holes on the roof bows. Test light!
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1956 L31
1961 L346 L347
1963 L380 L289

[Eric&Barb]

Down at the bottom of all the bus wiring diagrams is a chart for converting the wiring gauges from metric on each wiring diagram to SAE wiring gauges.
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In Stereo, Where Available!

[BarryL]

Put your meter on 12vdc and ground the negative probe. Use the plus probe to touch the toggle on the speedo pod both wires. If both wires show 12v then probe the wire at the dome fixture. If both wires don't work put a jumper to connect the two wires and continue on to the dome wire. If dome wire is 12v then clean up the dome fixture. Like others say make the ground good at the mounting screws. Like others say make the dome light on-off switch contacts clean and touching good.

[DadaCheese]

Thanks everyone!
(Jeler, johny__utah, Eric&Barb, BarryL)

Was indeed as easy as cleaning things up and using some dielectric grease on the dome light grounding screws.
Got out both my volt meter and simple test light too; voltage was correct all the way through after cleaning connections on the front cab switch, and the dome light.
SO pleased that there was nothing wrong with the front to back wire. Front cab switch was fine too.

Look at how rusty the grounding screws get after 54 years!

_________________
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Dada as in dadaism.
Cheese as in the stuff I love to eat.

[Eric&Barb]

Thanks for the update! Good to hear it was only a cleaning of connections that was needed.
_________________
In Stereo, Where Available!

[Jeler]

Awesome, great job! Thanks for the update!