Only 2 wires and I'm lost

[DryFly]

I confess, 12v and I don't get along.
I wanted to get my entry light working on my 72 Argosy, so I tried removing the bulb and the whole assembly fell apart. I guess 41 years in Argosy life is probably around 100 in human life. Anyway, I figured no big deal, I'll just get a tail light bulb holder from my favorite auto parts store, solder the wires up and I'm good to go. Nope.
Here's the set up - I have a white and black wire coming through the shell. A switch is next to the door on the inside and it works. I get about 13v dc when I hook the tester up to the wires - switch on, 13v, switch off, 0. It appears that black is hot and white is neutral.
I figured I should be able to touch the black wire to the butt end of a 12v bulb and the white wire to the shell and have the bulb light up. That didn't work so I then soldered the wires to the bulb and flipped the switch and no light. Thinking I had things backwards, I reversed the wires and again no light. I've tried this with 2 other bulbs and no light.
I must be over thinking this. The switch works, I get plenty of juice to the wires, but I can't get a bulb to light up. What am I doing wrong?
Here's a pic of the exterior that I'm referring to. I've crimped on the connectors so that I wouldn't loose the wires in back into the shell, and covered them with electrical tape to prevent arcing. Thanks for looking.

[Thisisliving]

Humm try the back to the bulb and ground the body to the the frame. If you have 13v the wire you should be good. The body acts as a ground. The white should be a ground thats hooked to the switch. Try that and see what happends.

[overlander63]

When you reversed the wires you probably blew a fuse. Recheck for 12v.
The black wire is power, the white wire is ground, notmneutral. Neutral is for 120 v. The black wire would go on the end of the bulb, and the white wire will ground the side of the bulb.

[RM66caravel]

Basic elect power good? Yes switch good? Yes bulb good? Yes does ground equal ground or wire good? Been doing this a while

[Wazbro]

It is possible you have a bad connection where you have voltage but no current (voltage reading then as soon as there is a load, connection is lost).

[DryFly]

Originally Posted by Wazbro

It is possible you have a bad connection where you have voltage but no current (voltage reading then as soon as there is a load, connection is lost).

That's possible? How do I test for that?

[Wazbro]

Originally Posted by DryFly

That's possible? How do I test for that?

Yes. Try checking the voltage while the light is hooked up.

I just found a poor connection on a trailer, the fuse for the fridge came apart and with a nonworking load (the fridge) the reading at the output side of the fuse was 2 volts.

[rogerdodger]

Also, a switch can show 12 volts, but under load, will not work. You may need to remove the switch from interior wall and check connections there, and test the switch. I replaced my switches with ones that have a light when on so I don't leave on accidently. Also, I may still have the old switches if you need one. Let me know and I can pop it into the mail.

[Mcdenny]

The bulb doesn't care which is + and which is -. I agree with the poster above, I bet you blew a fuse fooling around with the wires.

[Thisisliving]

NA I bet you lost your ground. You would get a positive reading on your volt meter. But without a ground to complete the circuit the light would not work. Try black to bulb and run a ground wire to the trailer skin.

[rayandre]

Did you get this light to work? I'm having the same problem only ours is a 69/70 unit with a brown and black wire. Having a devil of a time getting it work again. Worked prior to polishing and now I'm stumped like you were!

[DryFly]

I did get it to work. Ill try to post photos of my fix tomorrow.