BA15D double filament LED replacements?

[Ryban]

I have a few old brass light fixtures on my boat that have rockers switches on the back to toggle between a low brightness and high brightness mode. They're a BA15 bayonet incandescent bulb with two filaments. The two posts at the bottom are both NEGATIVE and the case/socket is positive.

For the life of me, I cannot find an LED replacement for these guys. I can't even figure out what they're called. They're not automotive BAY15D bulbs, because the prongs sticking out the side are not offset, but more importantly, those bulbs have dual POSITIVE posts at the bottom.

Can anyone help guide me to the right part name?

[Spot]

The fixture might be wired backwards (positive at conventional negative), incandescent lights do not care but inexpensive solid state electronics do. I have an old thread where I burned up a USB charging plug by hooking it to 12v socket that I 'tested' with an incandescent probe....

My boat has both marine-style BA15D for the old school running lights where the case does nothing and BA15S (like an automotive 1156) for the cabin lights where the case is negative. I would expect a two filament bulb to be indexed so BA_15D where the space is the indexing type like Y (like an automotive 1157) or U or maybe even Z. I read about something called a SBC-B15 that may have been used in table lamps but nothing there about dual filaments. My RV has one light that dims via the switch and it is just two single filament bulbs and the switch is off, 1 bulb on, or two bulbs on.

Could you post pictures of the fixture and bulb please?

[W32PAMELA]

Have you tried contacting Marinbeam? They should have a replacement that will work for you although not with necessarily with dual brightness.

[Spot]

Seems like there may be some special BA15D S8 bulbs that have two filaments.
Note the caveat about wiring
You would have to pin down the LED bulb maker to be sure that it functions as desired. Some LED sites use the base as the primary cross reference and then cross to other bulbs with that base that may or may not be the same electrically.

In the picture below, the 1176 and the 7240 look promising.

[Ryban]

Originally Posted by Spot

The fixture might be wired backwards (positive at conventional negative), incandescent lights do not care but inexpensive solid state electronics do. I have an old thread where I burned up a USB charging plug by hooking it to 12v socket that I 'tested' with an incandescent probe....

Oh boy, do I feel dumb that I didn't consider this. Indeed, when previous owner, the man who built the boat, installed the lights, he wired them backwards -- which as you noted, didn't matter for filament bulbs.

I re-wired both of the two offending fixtures, and they now work with BAY15D bulbs that I filed one prong down on.

Thanks for all the help!

[Spot]

Originally Posted by Ryban

Oh boy, do I feel dumb that I didn't consider this. Indeed, when previous owner, the man who built the boat, installed the lights, he wired them backwards -- which as you noted, didn't matter for filament bulbs.

I re-wired both of the two offending fixtures, and they now work with BAY15D bulbs that I filed one prong down on.

Thanks for all the help!

You are welcome. The idea to remove the one offending indexing prong on a BAY15D LED bulb to make it work for this project is outstanding. Any other solution would have required more new parts and/or more assembly. A 2 function (high/low) LED bulb with a plain BA15D base with a case ground was not available from my vendor.