Circuit question.

[parared]

Hi All! Me again!

So, I was installing a nice battery, testing the shore power transformer, and generally chasing circuits. Bow and stern lights are controlled by switches just inside the cable, to the left as you descend. There are two other switches there, one of which is involved with the mast head lights. In the cabin, at the foot of the mast, I see a dual-pull dual-throw switch, which seems to be switching output voltage for the mast head lamps between two inputs, one of which comes from that switch near the bow/stern switches. Does anyone know what the alternate power feed is supposed to be? Also, I have 3 wires going up the mast ( plus an antenna line ). Fine, I figure, looks like a fore and aft lamp up there, must be two hots and a common ground. But, I measure low resistance ( a couple of ohms ) between them all. ( I expected low resistance between each feed and the ground, but an open between the two feeds. As a matter of fact, I was using this expectation to figure out which was the ground ) Anyone know what's happening at the top of the mast?

Thanks!

[FranS]

So Im thinking right about now you wished you had checked out those circuits before you raised the mast

[EmergencyExit]

Wonder if it's just a setup to control the mast lighting from either the rear switch or the forward switch. Like at either end of the hallway of a house, etc. Those use a special switch and extra wire.

Maybe somebody rigged a circuit to emulate that with 12vdc switches ? One of the 2 switches at the forward position would negate the rear switch, and the other would activate the lights.

[parared]

Wonder if it's just a setup to control the mast lighting from either the rear switch or the forward switch. Like at either end of the hallway of a house, etc.

I was thinking that too, but it doesn't quite look like that. With wires disappearing into the hull, I can't be sure, but I did try switching them like a 3-way, and didn't find the output voltage to be controlled in that fashion. Hmm, well at least not until right now ... I wonder if they are wired like that, but fed backwards in one position from the other. Hmmm, sigh, time to map the thing.

So Im thinking right about now you wished you had checked out those circuits before you raised the mast

I'm almost certain I'll have a shot at her with the mast down before she gets to the mooring .

[Andiron120]

I am in the process of rewiring my 77 C-22 at this time also and from your description I suspect what original installer might have had in mind is this. The forward lamp is needed when operating at night under power, " steaming light", and you need a 360 white light for an anchor light. What you have may be a setup to switch between the forward being lit and both being on. I have a steaming light, forward deck light combination on my 77 and they are on seperate switches, I have added a 360 white to the top for an anchor light.
After looking the rest of mine over I started from scratch.

[kokezaru]

I think you are going to have to take a look at that mast head.
There are a few different configurations of nav lights for sailboats on the mast:

1) Port and starboard nav lights at the mast head

2) Port and starboard nav lights, with a stern light also at the mast head.

3) Red over green all around lights at the mast head

In addition, you can also have an anchor light.
My C26 also has a pair of deck lights mounted on the lower spreaders, which adds more wires.

[parared]

Duh ... I start thinking about this, and realize that of course the 3 wires will see low common resistance. Two pair will see the resistance of a single filament, while the other pair will see the resistance of both filaments. So, I just need to find which pairing measures the sum of the other two pairings and that will tell me which is the common ground. Then ... label them somewhere .