I have been converting my coach from fluorescent/incandescent to LEDs. After installing strip LED's, I ordered cool-white BA !5D, the ones with side pegs at the same level and dual contacts on the bottom. When they arrived, I couldn't get them to work, even when switching polarity on the bottom. I learned that both contacts were positive, with the side being the ground. :-( When using a hot 12V wire on one contact, the light was moderate, when moved to the other contact, light was very bright. Anyway, they are worthless to me, as all my lamps use the + and - contacts. If anyone can use them, they can have them. I bought them new from eBay, so it's not easy to return them. There were 2 packs of 5 each for 10 overall. I live in Nacogdoches, so if you come to town, you can have them.
On a slightly related note, I have 5 (actually 4 3/4) packages, 5 meters (16') in each pkg of warm-white strip LED's. They are about 6 weeks old. Nothing wrong with them; my DW changed her mind and decided she preferred cool-white LED strips, so that's what I installed. :) I won't give these away, but will discount them appreciably.
If anyone is interested, you can contact me at hayfever39@gmail.com or call me at 936-554-0133
Don, lamps may be possible to rewire for socket side ground. Years ago we added a 3rd swing arm lamp and changed to 3-way switch. Let me know if we can help. Might be easy.
I had the exact same problem with my ebay BA15D bulbs for the swing arm lamps a couple of months ago. The ebay seller gladly took them back and even paid for return shipping. I replaced them with bulbs from another vendor that clearly labeled them as the right version and I've had no problems with them. I did have to slightly pry the contacts upwards inside the lamp socket so that they would make solid contact.
I don't know how to link to a previous thread but if you want to search for this title you will find more information by others on the BA15D's...
Swing Arm Lamp Bulbs?