Masthead Electrics

[Drew13440]

So, I've got a two way switch on the breaker box that controls anchor and steaming lights at the masthead. In the middle position, circuit is open (lights off). To the left is supposed to turn on steaming light, to the right, the anchor light.

I put the mast up this spring and carefully cleaned the three-pronged deck connection. Trouble is, I get the anchor light with the switch in both positions, left or right. Any ideas on what is up? :neutral:

Thanks for any insight.

 

[Bill Roosa]

Ground problem

Assuming that three wires are all you have to deal with (anchor power, steaming light power and common ground) you can wire it so that either it works right or both are on at the same time. No other way to do it. But since you say you can turn on one or both it sounds like you have a ground wire problem up the mast.
First things first though, pull the plug at the mast base and confirm that you have the following on the boat side of the plug 1) a lack of continuity between all possible (3 total) combinations of wires with the switch off. 2) That one and only one of the wires is a ground and that you can't "switch it OFF". 3) Switch to steaming and confirm that one and only one of the other wires is hot to your ground wire, repeat same after switching CB to anchor (it must be the other wire and ground BTW).
If all that checks out then the problem is up the mast. Switch to the mast side of the plug. You should get (dang gota do some math V=IR, R=VI, let’s see 12 volts and probably 1 amp light so 12/1=12 ohms plus the wire up and back say another ohm or) 13ish ohms resistance between the ground wire and each of the power wires. You can tell which wire is the ground from what you found while testing the boat side of the plug or note the color of the wire. Green is the typical color for a ground but black is used a lot also. You should get 26ish ohms between the two hot wires (reading hot to hot via a common ground connection up the mast includes both bulbs) and you should get infinite ohms between the mast’s metal and all the wires.
We really can't diagnose it without knowing what the wires are doing up the mast so go get busy and let us know what you find.

 

[Drew13440]

Thanks Bill, I'll check it out. Three wires for sure, two positives and a ground. Reading your post, it occurs to me that both lights may be on at the same time - it's hard to tell from the deck, but it's a pretty bright 360 for sure. Will let you know.

 

[John23883]

Mast light

You are correct, when you have the steaming light on it is the forward portion of the light, 225 deg. When you switch to anchor it adds the stern portion 135 deg. for 360 deg. of light, so yes both are lit in that position.

 

[Drew13440]

Reviving this one

OK, so at the deck fitting, everything checks out. One hot wire in the "steam position," two hot at "anchor." So it's up the mast. Is it possible that water build up in the fixture could cause this, or is it a wiring issue? It's a new problem, everything was hunky dory last year. Thanks again...