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Ok, needing some help here. Bow light was not working on my 1987 Montauk, so I pulled it apart. The old set up consisted of a single bulb (no socket) with one wire soldered to the single contact on bottom and one to the side. Those connections had deteriorated so I removed it. Purchased the Perko double contact bayonet socket (0052DP) with a #90 led bulb as seen in the photo. Also tried an 1142 bulb.

No matter what I do, I can't get the bulb to light. The switch, bulb, and socket all work perfectly fine - I have tested them separately. Is the problem with the socket/bulb I am using, or, is there not enough voltage? One multimeter I have has the wires at about 7 volts while another multimeter gives me a reading of 11 volts. So I'm really confused as to what the problem is. Any advice would be highly appreciated. Thanks.

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Hi Rnissin,
A couple of thoughts:

1. I assume you have tried reversing the leads on the new LED bulb/socket assembly as you connect them to the boat wires. LEDs will only work when wired with the correct polarity.

2. Your meter readings are troubling. Does one meter consistently read 4 volts less than the other? If so, one of them is obviously bad, either in the meter or corrosion/connection problem in the leads. If digital, it would be more likely the leads.
If after a number of attempts with each meter you find that both read inconsistently, then you might have a marginal wiring connection at some point along the path. You should try taking the readings again at the terminal block in the back where the wiring enters the gunwale/rubrail.

Dennis

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Hi, Dennis:

Thanks for the reply. Yes, I did reverse the leads but no luck.

The meter giving me the 11 volt reading (really more like 10.8 or so) is digital. The other you can see in the photo attached here. I did not try to get a reading at the block but that's probably a good idea.

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Hi rnissin,
I looked up DR LED's GE90 bulb specs, and saw it had a max draw of .12A. Assuming your battery is still in the aft, perhaps you have 40' of round trip wiring. This gives a calculated voltage drop of:

4.016 milliohms/ft * 40 ft * .12A = 19.3mV

Just accounting for wiring drop only, you should really see battery voltage at the LED socket. Throw in another 20' for the switch run and you still only have 30mV drop. I'd start tracing backwards to see where you are losing the volt+.

That being said, the bulb should still light with 11 volts, so I'd bet this is not the problem. Have you tried putting your (good) meter probes right inside of the hot socket to see the 10.8V, switching on and off to verify the switch operation?

Dennis

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Excellent information, Dennis. Thanks!

Let me be clear about what I do and don't see...

When I use the multimeter on the bare bow light wiring, I put the red probe on the right wire and the black probe I touch to the metal light base or even the bow rail. When I do this, I get a reading of about 11volts on the digital multimeter. The other multimeter gives the reading you see in the photo.

When I turn the switch on, I get a reading. Off I get nothing. So I know the switch works.

If I put the probes on both wires I get nothing. Red on right, black on left, it doesn't matter. I only get a reading if I ground the black probe with the red probe on the right wire.

When I attach the socket to the wires, I get no reading inside of it no matter what I do -- wire to wire, ground one attach the other, etc. However, I have touched the wires from the new socket to the inside of my stern light socket and it lights right up. That's how I know the socket and bulb work.

I hope this all makes sense!

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Well, it makes sense and no sense..., so I'm going out on a limb here.

I suspect your light was modified. If you get 11V between one of the wire leads and the fixture base or the bow rail, perhaps a previous owner used the bow rail to carry one side of the path when a wire failed. I had a 1988 Montauk until this spring. I believe the front navigation light used a festoon type bulb in a proper holder. It did not have one of the wire leads soldered directly to the bulb.

Have you tried removing the entire base to see what is underneath? If this has been modified as I suspect, I would guess you might find a path on the bottom which somehow gets to the bow rail. There is a metal plate under the gel where the norman pin mounts, perhaps that is the location.

At any rate, I also hope this suspected modification has the exposed bow rail as ground or things could get interesting in a dangerous sort of way.

You should look in the back at the terminal block to see what is there. Both wires should enter the hull at that point. You can do a continuity test to verify that one wire makes a good connection to the bow and the other doesn't. Look back there and see what you find.

Interesting problem.
Dennis