Only one wire?

I have two sets of old Dick Cepek lights that I took off an old 80's style rollbar, and I want to see if they work. They only have one wirecoming out of the housing. I opened one light up to check it out, and it looks like the bulb may be grounded by the metal housing. Anyboby seen this before? I'm no lighting guy, so maybe it's common? Can I just safely hook up the one wire to power?

 

[Robb]

Yes, they are grounded through the casing. Single wire gets +12v

Robb

 

[Alec]

If the mounting surface for the lights isn't a good ground, then extend a grounding wire from the light's bolt to a good grounding surface.

 

[mattadams]

I've seen it before, but I don't think its the preferred way to go! For instance I couldn't ground my lights that way, since they are mounted to a surface which is line-x'ed. In order for that to work, you would have to have exposed metal (no paint) at the base.

 

[RangerX]

Okay, thanks. I just want to test and see if they work, without fear of explosion. If they do, they are going on Ebay.