masthead lighting problem

[rbtpfe9]

I am completely befuddeled by my masthead light. It won''t work. I have checked current before it goes into the mast and it registers on voltage meter, current registers when I place probes on masthead light but when I insert light it does not burn. Light is good. Also, when masthead lightbulb is removed light illuminating down on deck barely burns but when I put bulb in the deck light goes completely out. Any ideas?

[rbtpfe9]

Light referenced above is my steaming light/deck light combination - have not made up to the top of the mast yet to see why that light doesn''t burn either.

[CherylannJohn]

In a similar problem, but not on a mast, it turned off to be a faulty ground. Reading with a meter looked like it was a good ground.

Cleaned and reattached all connections from the light to ground and it fixed the problem.

A Guess,

John

[halyardz]

I had the same problem on my Tartan 33 (52'' mast). It was very frustrating. So last year we pulled the mast and rewired the rascal with two 3-16 feeds...one to masthead where we also installed a tri-color, and other to steaming/deck. The existing wire was totally messed up...bare spots, no logic to connections etc. Works fine now and peace of mind is priceless. Jim

[Edel-665]

I''d take a bit of emery cloth and polish up the contacts on the bulb. As you mentioned, when you put the bulb in another fixture, it fails there also.

HalayrdZ, You netioned that you rewired with 3/16. You realize, you''ve rewired with undersized wire. In order to get the proper 3% voltage drop limit, you should have used 12awg wire. Voltage drop for nav lights (and other critical circuits is to be limited to 3%, which in your situation calls for 12 awg ideally and 14 awg at minimum)

[c25]

Edel,

I was going to mention the same thing (3/16 to small in halyardz''s application), but was rushed when I first saw the post. I just re-wired my 30 foot mast and was on the ragged edge (a bit over) of 16 gauge vs 14 gauge...I went with 14. Another word of advice..don''t rely on the West Marine Catalog wire estimating charts...they''re wrong...actually they don''t have fine enough resolution & this leads to errors. As for wire...Hamilton Marine in Maine had good prices on marine wire in 100'' spools.

[Edel-665]

C25,

I don''t use the West Marine catalogue for wire sizing. I use a combination of "Boatowner''s Mechanical and Electrical Manual" and an application called Wiresizer 2.0. It''s a great little app, you can play with the % voltage drop, the gauge, and the reference voltage.

the site for wiresizer seems to be messsed up these days. If you''re interested let me know and I''ll email you the application.

[halyardz]

c25 has got a point...3/14 would be better to run to the masthead and also agree that 100'' or larger spools is the way to go.

[39512]

Sounds like a polarity problem.