Navigation Lamp

[IJA38]

Im having my cratch board replaced as the one that came with the boat I bought was beyond repair. It meant removing a rather ugly navigation lamp, so I thought great time to spruce up.

 

I have been given an old car lamp. I was confused when I saw that it only had 1 lead coming out of it (brown) so I now assume the lamp is designed to work on negative earth. How can I rewire it to work as a boat lamp? It is quite striking.

 

Cheers

 

Ian J

[AllanD]

It would depend on the type of bulb it uses. If it has a bayonet fixing then perhaps soldering a negative return lead onto the lamp casing could be a solution.

[spadefoot]

Just use some kind of connection to the casing as the negative. Do not let the casing touch the metal of the boat.

[MankySteve]

Is there a internal bolt connected to the chassis of unit? undo bolt clean up contact area and just install a ring terminal and suitable sized earth cable. If no bolt available any tabs or such in side unit that could be drilled though and bolt, nut, ring terminal and locking nut

Edited June 29, 2016 by MankySteve

[NickF]

So if the casing forms part of the wiring and there is a current flowing. i.e.the light is on, what happens if you touch the light casing and a metal part of the boat at the same time, do you get a shock? I guess not otherwise you would get a shock from a car but i can't quite see why not?

[Chewbacka]

So if the casing forms part of the wiring and there is a current flowing. i.e.the light is on, what happens if you touch the light casing and a metal part of the boat at the same time, do you get a shock? I guess not otherwise you would get a shock from a car but i can't quite see why not?

Two reasons, firstly the casing is connected to the battery negative through a wire as is the metal body of the boat, so there is almost no voltage difference, and secondly if the earth wire were to detach from the lamp casing the case would be 12v above the hull, however you will not really feel 12v through your finger.

[Tony Brooks]

So if the casing forms part of the wiring and there is a current flowing. i.e.the light is on, what happens if you touch the light casing and a metal part of the boat at the same time, do you get a shock? I guess not otherwise you would get a shock from a car but i can't quite see why not?

 

The resistance of "normal" skin is high enough to prevent 12 or 24 volts flowing through it. Usually even when damp/wet. This allows the skin to act like the insulator on a cable.

 

Do not try it on your tongue or other areas to thin wet skin. If you do you will feel it at 24 volts it could be rather unpleasant.

[Sea Dog]

Is there a internal bolt connected to the chassis of unit? undo bolt clean up contact area and just install a ring terminal and suitable sized earth cable. If no bolt available any tabs or such in side unit that could be drilled though and bolt, nut, ring terminal and locking nut

Which sounds like a good idea, it's how the lamp worked in its original car setting, and the lamp would work, but using the hull as an earth return is a bad thing in boats (it's a big subject, so search on here or Google if you need to verify). The OP should modify the lamp to a 2 wire system, preferably with the -ve also separate from the lamp chassis.

[David Mack]

Can you change the lampholder in the fitting for one which has two terminals and is insulated from the body? Or maybe there is such a fitting already with an earth strap from one terminal to the body, in which case all you have to do is remove the earth strap.

[ditchcrawler]

If you are mounting the lamp on a wooden cratch board then you don't really have a problem

[IJA38]

Thanks all- I wil get on with it- now I know what to do