Electrical anomaly

Carter Brey · Post by **Carter Brey** » Apr 20th, '05, 17:52

I've been deep in prelaunch prep this week, and the other day I climbed
the mast to replace the steaming light bulb with a bulb of slightly
higher wattage in the OEM steaming light/deck light unit on my CD25.
This is the integrated unit with which most of you will be familiar.

When I finally remembered to check the light this morning, I saw
something that had me totally perplexed. When I switched on the
steaming light, the deck light immediately beneath seemed also to
be illuminated, but faintly. It did not seem to be shine-through, which
I think would be impossible, given the design of the unit. When I
turned off the steaming light and turned on just the deck light, the
deck light shone at its usual brilliance.

My question is this: is this supposed to be a feature of this unit?
In other words, does the deck light come on faintly to indicate that the
steaming light, which from the deck is impossible to see, is operational?
Or is there some kind of odd cross current happening? I don't remember
this happening before-- I may simply have missed it, I just don't know;
I almost never used the steaming light before.

I didn't do anything on Monday other than to climb up, unscrew the
housing over the steaming light, remove the unit containing the bulb,
replace the bulb, and screw the housing back down. No wiring stuff. No
monkeying with the distribution panel.

Just wanted a little information before climbing up there again.

Thanks,
Carter

yves feder w1ux · Post by **yves feder w1ux** » Apr 20th, '05, 19:18

I wonder Carter, if this occured with the lower wattage bulb as well?

Might be hard to tell if something happened to the wiring over the winter - drawing more current with the higher wattage steaming light could THEORETICALLY have overloaded the wiring - perhaps causing a partial short to the other positive lead (the one to the deck light)

If it was/is a high resistance path, then the deck light wouldn't see the full 12V, and not have full brilliance.

Then when you turn on the deck light switch, of course the deck light sees the full 12V and has normal brilliance.

What happenes if you turn on the steaming light AND the deck light switches at the same time - hopefully the deck light would be at full brilliance.

One way to check would be with an ohmeter - see if there is a leakage path between the two 12V conductors.

Use the multimeter in the voltage position as well, and see if voltage appears on the distal side of the deck light switch when it is OFF and when the steaming light switch is on - you might also check to see if there is voltage on the steaming light switch when it is off, and the deck light switch is on -

All of which is only to see where the leakage path is. If only part of one strand of the wire is touching, say somewhere in the mast, it could cause what you're describing.

A head scratcher, I'm afraid....

Y.

Carter Brey · Post by **Carter Brey** » Apr 20th, '05, 20:45

Yves,

That sounds good-- I'll check on Friday when I go back up to the Island. Thanks!

CB

Oswego John · Post by **Oswego John** » Apr 20th, '05, 21:14

Yves and all,

First things first. How and where did you resurect the word "Distal". I haven't heard that word used since Hector was a pup. It's a good one , though.

Getting back to Carter's problem, I agree with the course of troubleshooting action that you suggested. A long shot idea first came to mind when I read of the deck light glowing at half brilliance when the steaming light is switched on. This is a classic example of the deck light bulb being in a series path to ground for the steaming light return.

Of course, until proper voltage and ohmage tests are complete, anything we presuppose is purely conjectural. And like you say, those little stray whiskers of stranded wire can really do a number on a persons sanity. Ergo, break out the multimeter ASAP.

Happy testing,

O J

Mark Yashinsky · Post by **Mark Yashinsky** » Apr 20th, '05, 22:35

Where are you that you cannot check the steaming light? Even if you have to walk over a couple of docks (no, it does not have to be directly ahead of the boat), or get back into your boat tender and move away from the boat a bit, you should be able to see it.

Bet the ground side of the steaming got moved over to the hot side of the deck light and now have a series of steaming hot wire to steaming light, to deck light to ground. The deck comes into the middle of this and goes thru the deck light to ground. Did you have to disconnect any wires when changing the bulb or merely remove the lens and pop in a new bulb? Did you forceably clean the sockets and mangle something? Confirm by steaming switch cause both to faintly dim (really a 24v bulb on 12v) and the deck is full w/o ANY steaming light glowing).
Maybe and just maybe, the steaming light ground got moved over to the mast and there is a high resistance to battery "-" thru the mast, to the step and so on. Check this by seeing if the light, and ONLY the correct light comes on, regardless of brightness.

Mark Yashinsky · Post by **Mark Yashinsky** » Apr 20th, '05, 22:37

maybe its just the Naval equivalent of gremlins (not the movie).

Carter Brey · Post by **Carter Brey** » Apr 21st, '05, 06:15

Mark Yashinsky wrote:Where are you that you cannot check the steaming light? Even if you have to walk over a couple of docks (no, it does not have to be directly ahead of the boat), or get back into your boat tender and move away from the boat a bit, you should be able to see it.

Bet the ground side of the steaming got moved over to the hot side of the deck light and now have a series of steaming hot wire to steaming light, to deck light to ground. The deck comes into the middle of this and goes thru the deck light to ground. Did you have to disconnect any wires when changing the bulb or merely remove the lens and pop in a new bulb? Did you forceably clean the sockets and mangle something? Confirm by steaming switch cause both to faintly dim (really a 24v bulb on 12v) and the deck is full w/o ANY steaming light glowing).
Maybe and just maybe, the steaming light ground got moved over to the mast and there is a high resistance to battery "-" thru the mast, to the step and so on. Check this by seeing if the light, and ONLY the correct light comes on, regardless of brightness.

Hi Mark--

What I meant was that if you are actually on board the boat, the steaming light can be difficult to see. The boat is currently on the hard, so to check things I have to climb on board, switch something on, climb down, and walk forward of the boat a few paces. Sorry that was obscure.

Yes, to answer your question: when the steaming light switch is on, both glow dimly. When the deck light switch is on, only the deck light is on, and at full brilliance.

You and Oswego John said basically the same thing, which was my fear as well-- so when I get back to the boat yard on Friday I'll do some multimeter tests.

All I did was to remove the lens and pop in a bulb, but in doing so I did gently pull the socket out, so it's quite possible that, as you conjecture, something might have gotten mangled. But if I'm lucky, the problem will be traceable to some of the wiring I did inside the DC panel late last season.

Thanks to all of you for the help.

CB

Warren Kaplan · Post by **Warren Kaplan** » Apr 21st, '05, 06:41

Carter,
Time to put on your marine electrician's hat. I had a similar problem back in 2001. Put these words into the search function on this board. Mast Short Circuit. You'll get a whole bunch of threads on this. About 4 threads down you'll see Troubleshooting Mast Lights which I had the frustration of having to deal with. Lots of info there including, if memory serves, some methodology in using a multimeter to sort this all out. Hopefully I won't hear some sort of primal scream of frustration emanating from City Island late Friday as I sit 20 miles away in Oyster Bay.

The Cape Dory Board