1 Topic by mokshaSF (edited by mokshaSF 2014-04-13 22:09:36)

  • Registered: 2014-03-31
  • Posts: 15

Topic: mast lights don't work

I realize there's a recent post dealing with mast wiring...

My situation is a little different in that I would like to use the existing wiring if only I could understand it.

At the moment, the mast lights don't work.

What I find in my boat are 4 wires (white (grd), yellow, green, and blue) running from the panel to a female socket at the base of the mast. This socket tests fine with the voltmeter.

Coming down from the mast are only 3 wires that don't match the colors listed above. It seems the socket has one prong slightly larger than the others so that it will only fit together in one position. That larger prong seems to be for ground and in this case has no wire attached to it from the mast.

That leaves 3 possible reasons why the lights don't work -

1.The lights are grounded by the mast but coincidentally the anchor and steaming light bulbs need replacing (and maybe a third light)

2.One of the wires is ground but goes to the wrong prong.

3.I need a ground wire to the light fixtures.

If anyone has any enlightening (pun intended) input I would be grateful!

Any thoughts that might inform and/or enlighten the situation would be appreciated!

Meantime, I'll try to find out if one of those wires is actually for ground. That would be easier than going up the mast to check a light bulb...

2 Reply by Ian Malcolm (edited by Ian Malcolm 2014-04-14 03:42:41)

  • Registered: 2006-09-20
  • Posts: 175

Re: mast lights don't work

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  • Veteran Member
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  • From: Burlington, Ontario
  • Registered: 2005-06-12
  • Posts: 63

Re: mast lights don't work

If you only have the anchor and steaming lights on your mast, it's possible that there is a separate negative (ground) for each light. If you have a tri-color mast light (as well as a steaming light) then you probably have a shared negative wire. In either case a test of the continuity from each bulb socket to the connector at the base will tell you. Another note, if you have LED bulbs, keep an eye on the polarity of the sockets. a lot of LED bulbs and light fixtures are polarity sensitive (only work one way).

.                               ,,,,,
                               (o o)
------------------oOO---(_)---OOo------------------
  • Registered: 2014-03-31
  • Posts: 15

Re: mast lights don't work

Thanks much for the advice. I'll go checking the next time I'm on the boat which I hope is very soon.

5 Reply by Ian Malcolm (edited by Ian Malcolm 2014-04-14 13:53:38)

  • Registered: 2006-09-20
  • Posts: 175

Re: mast lights don't work

N.B. an ohmmeter *WONT* check LED lights.   They typically wont start passing significant current till they have 8 or 9V across them.   If you have any LED lights, you need to test them with a 12V supply + a 21W car bulb or a 3A circuit breaker in series to limit the current if there is a short circuit, and actually look up the mast to see if they are on.

  • From: Montreal
  • Registered: 2005-04-22
  • Posts: 259

Re: mast lights don't work

Good tips Ian!  That one about the LEDs was a new one for me!

  • Registered: 2006-09-20
  • Posts: 175

Re: mast lights don't work

  • Registered: 2014-03-31
  • Posts: 15

Re: mast lights don't work

Ok, I visited the boat today and checked the resistance of the 3 wires coming from the mast - the colors btw are black, white, and green.

Ian asked for the readings of the different combinations in ohms.

My meter isn't super accurate - its the type with a dial.

with the probes of the meter shorted I got 1 ohm.

Green to white - 150 ohms

Green to black - 35 ohms

Black to white - 40 ohms

Can it be deduced from this that black is ground?

9 Reply by Ian Malcolm (edited by Ian Malcolm 2014-04-17 04:56:26)

  • Registered: 2006-09-20
  • Posts: 175

Re: mast lights don't work

       2
     V
P = ---
     R
  • Registered: 2014-03-31
  • Posts: 15

Re: mast lights don't work

Thanks Ian,

Your post is the Physics class I never had but wanted! I'll fill in the chart with a proper meter this time.

I'm not 100% certain about the bulb type or anything else on this boat. I'll assume they are "conventional" for the time being.

The next wave of tests ought to give an answer.

Hoping to be back on the boat in the next couple of days.