Replacing the LR 12VDC ceiling light, light bulbs blow out.

[SaSuVa]

1995 Damon UltraSport Class A, 34', gasser.

I replaced the 4 bulb older style ceiling light fixtures(2ea) with 2 fixtures that had 2 bulbs per fixture. There is a black and white wire from the RV, hot and neutral, and a black and white wire on the fixture.
I wire nutted them together, white-white, black-black and got two really, really bright 1076 bulbs that lasted about two weeks with intermittent use, then they blew. I test the voltage, and it was 11.78VDC last time, and each time about the same. Never a surge or a spike, just steady really bright till they blow out.

Both ceiling fixtures are exactly the same, and have exactly the same issue.

I have put 20 bulbs into the fixtures, and during that time I have taken the fixtures down and tested the wiring, voltage orientation in the fixture... and exactly the same results. The outside of the bulb holder is negative, the inside has two contact points for the bulb's two contact points. One is positive, the other has nothing.

The fixture is a 10" bright brass fixture with diffuser, here... 12V RV CAMPER BRASS CEILING LIGHT W/ GLASS & SWITCH - eBay (item 170355331890 end time Feb-28-11 07:24:07 PST)

Before the new fixtures were installed, no problems, except the lead and glass were coming apart. Electric and the old bulbs, not 1076, were fine, had to dust 'em every so once in awhile...

I should add there is no other 12v or 120v electrical issue in the RV.
???
Sam

[nbounder]

sounds like you installed bulbs that run a LOT hotter than the older ones. The hotter the bulb, the shorter the lifetime. Also, the hotter the bulb, the more risk of fire. If I am correct on that fixture, it has a sheet of insulation at the top. This actually traps the bulb heat and causes earlier failure. Change back to lower wattage bulbs and tell us the result.

[SaSuVa]

Thank you for the quick reply, nbounder,

I am not sure I follow, the 1076 12V DC bulb is the only bulb that is recommended by the fixture manufacture.

What do you recommend? Please let me know, as well as a link to the recommendation, thank you,
Sam

[RVhauler]

Would recheck the bulb numbers or if you have a like fixture check the bulb numbers from that. that number doesn't sound correct IMO

[SaSuVa]

Yep, took me back as well, thought I would be able to use the 1157's I had in the old fixture, nope.

The new fixture socket and label are designed for a 107612V bulb, with two contacts, and flat bayonet pins. The 1157 have offset bayonet pins.

I have two exact fixtures, and they both have identical labels, and they both have identical problems.

At least I know it is not a simple camper blunder, this far.., please keep the ideas coming.

Thanks,
Sam

[two slides]

Quote:

Originally Posted by SaSuVa Yep, took me back as well, thought I would be able to use the 1157's I had in the old fixture, nope. The new fixture socket and label are designed for a 107612V bulb, with two contacts, and flat bayonet pins. The 1157 have offset bayonet pins. I have two exact fixtures, and they both have identical labels, and they both have identical problems. At least I know it is not a simple camper blunder, this far.., please keep the ideas coming. Thanks, Sam

why don't you install flourescent lite fixtures----they should put out more lite & last longer. I installed them on a 1990 rv I had & they worked great.
if my memory is still working, #1157 is a brake lite/tail lite combo & bulb does get pretty hot with continueous use. suggestion: can you remove lite bulb cover (plastic lens) to let heat escape? if they last longer, they must be getting too hot.

[SaSuVa]

The lights are in the slide, so they are bright brass and fancy, and new, or not so new that they can be returned, but, well they are not so old that replacing them makes financial sense.
I have other lights, but these need to be nice... so I need to fix 'em.
The 1157 would probably be ok in the fixture, it is the 1076 I cannot keep in the fixture.

Replacing them is next though... good idea

Sam

[nbounder]

Any good auto store (O'Reilly, AutoZone, NAPA) will be able to tell you from the big books on the counter which bulb would be the next cooler one. I do not have the big book,, but at one time I found the info on the web somewhere. I'm sure a bunch of searches in Google would turn up the data. Do I understand that the 'new' bulbs had 2 bottom contacts but the socket had only one? PS - call the mfr of the fixture and give 'em hell - tell them you feel it is a fire hazard!!! Let THEM recommend a different bulb.

[DAN L]

Quote:

Originally Posted by SaSuVa 1995 Damon UltraSport Class A, 34', gasser. I replaced the 4 bulb older style ceiling light fixtures(2ea) with 2 fixtures that had 2 bulbs per fixture. There is a black and white wire from the RV, hot and neutral, and a black and white wire on the fixture. I wire nutted them together, white-white, black-black and got two really, really bright 1076 bulbs that lasted about two weeks with intermittent use, then they blew. I test the voltage, and it was 11.78VDC last time, and each time about the same. Never a surge or a spike, just steady really bright till they blow out. Both ceiling fixtures are exactly the same, and have exactly the same issue. I have put 20 bulbs into the fixtures, and during that time I have taken the fixtures down and tested the wiring, voltage orientation in the fixture... and exactly the same results. The outside of the bulb holder is negative, the inside has two contact points for the bulb's two contact points. One is positive, the other has nothing. The fixture is a 10" bright brass fixture with diffuser, here... 12V RV CAMPER BRASS CEILING LIGHT W/ GLASS & SWITCH - eBay (item 170355331890 end time Feb-28-11 07:24:07 PST) Before the new fixtures were installed, no problems, except the lead and glass were coming apart. Electric and the old bulbs, not 1076, were fine, had to dust 'em every so once in awhile... I should add there is no other 12v or 120v electrical issue in the RV. ??? Sam

i have a brass colored 2 bulb wall sconce with shade in the fwd slideout between the dinette and the couch. when the original lamps burnt out in apr 2008, i could not find replacement t- 1076 lamps locally.
i checked the socket with a vom and found that on the dual base lamp and socket, one contact was 12v power and the other was the ground. a strange design to say the least.
i bent one contact (the ground) up with angled needle nose pliers so that when a single contact lamp is installed in the socket, the side of the lamp base is in contact with the the socket contact i bent up. the other contact is 12v power. i bet this explanation is as clear as mud.
i am presently using 2ea 1141 lamps, but have used 1156 lamps.
now i can use several 12v single contact lamps ranging from 12 watts to 26.9 watts. 1003=12w, 1141=18w, 1156=26.9w. there are probably others but these are the ones i am familiar with.