Single Contact Bayonet Base

Hello -

I am re-wiring some of the lighting in my 1976 Egg Harbor, and I have found a single-contact bayonet base fixture in the shower (12V). Once I pulled it out, I saw that the actual light fixture only has a + wire running into it, and then the return wire is soldered to the fixture itself 3 inches away. Can anyone explain how/why this is? As far as I know, DC fixtures should be a complete circuit, but it seems here that there is a break because the + wire goes to the bulb and the bulb is not connected to the negative...

Thanks for any help/explanation!

-Patrick

 

Yikes !


Sounds like an automobile light fitting ?

I suggest you upgrade the wiring and socket

 

Sounds like the fixture is grounded and the installer is using it as the ground. For this to work the fixture would have to be mounted on something grounded or a fastener attaching it has a ground wire attached, probably on the back side.

The little solder button at the bottom of the bulb is the + and the surrounding socket is the -

This type bulb socket is automotive in origin and still pretty common, but the wiring has definitely got to go. Replace with multi strand copper duplex, tinned is best and sized appropriately for the load.

Steve

 

Have you ever tried touching the fixture while taking a shower?

 

Negative side of the circuit goes from the outer base of the bulb to the bulb holder to the metal light fixture to the wire soldered to the light fixture.

 

I never have tried touching it while in the shower - seems like the last place I would want a fixture with electricity running through it!

I am planning on pulling out the current bulb holder and putting in a double-contact bayonet. Seems safer and easier. Anyone see any issues with that?

 

If you're concerned about current draw, like you're going to spend time at anchor or drifting with engines off, you may want to consider LED's. A lot less juice to burn.

Steve

 

The double contact bulb holder also exists in 2 versions: the automotive one with a chassis ground lug and the insulated marine one, sometimes made from reinforced plastic to avoid corrosion.

 

I am planning on pulling out the current bulb holder and putting in a double-contact bayonet. Seems safer and easier. Anyone see any issues with that?


If you are willing to keep the grounding of the lamp thru the fixture case, it is then possible to add a switch and obtain 2 -3 levels of light.

Simply install an auto style tail light bulb and use the switch of your choice.

Stop usually 2A, run about 1/2 A .

 

Plastic double contact bulb socket