Assistance please on electrical short in light fixture

Topic: Assistance please on electrical short in light fixture (Read 4 times) previous topic - next topic

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December 24, 2012, 03:46:41 pm

Hey there everyone Merry Christmas/ Happy Holidays.
I was out wrapping christmas presents in my 1993tk ( I mean where else can you hide presents from curious children LOL) when I smelled electrical burning. Turned off all lights and then noticed that the light fixture in the ceiling by the closet had black smudges on it. This is a small fixture with one of those round bulbs in it.
I have not taken the fixture apart yet thought I would like to get some ideas from some of you more highly techinical people before I attempt it. Not sure where to begin.
What would cause this to occur all of a sudden? I am currently parked in Eastern Oregon and am at my daughters for the winter. I don't stay in the motorhome I have my own digs in the house. It has been snowing a little, then melting off. Temps are around 30 at night and 40+ during the day.
I leave a small oil heater running all the time to keep the motorhome above freezing inside. I have a temperature gauge that has a remote station that I keep in the house to be sure that the temps inside the rv stay stable.
Youe ideas and suggestions as to how to go about this will be gratefully appreciated.

Patricia The grandma of her tribe.

Re: Assistance please on electrical short in light fixture

Reply #1 – December 24, 2012, 04:36:33 pm

Yahoo Message Number: 135839

Quote

Hey there everyone Merry Christmas/ Happy Holidays.
"...when I smelled electrical burning. Turned off all lights and then noticed that the light fixture in the ceiling by the closet..."
Youe ideas and suggestions as to how to go about this will be gratefully appreciated.

Patricia The grandma of her tribe.

Pat
Question --- Was the suspect light 'on' when you smelled the burning??
Ideally it would have been benificial if you could have observed smoke from whatever the source, that fixture or some other.
While not such a good activity, particularly at this time, I would, at the very least, remove the plastic lens and the bulb. Carefully observe any signs of burning. Then, when you have more time, remove the fixture (a couple of screws) and examine the wiring for indications of burning. You might also look for signs of water intrusion.

Good Luck, Merry Christmas, and keep us posted.

Steve S.
Lazy Bones & Jiggs

Re: Assistance please on electrical short in light fixture

Reply #2 – December 25, 2012, 10:20:04 am

Yahoo Message Number: 135841

Hi Steve, thanks for your reply.
I took the lense off and the light was on when I smelled the burning and did see smoke. The switch is sooty so I guess I will take the bulb out next. Do I need to turn off all of the electricty before I take the screws out to inspect the wiring?

Patricia

Re: Assistance please on electrical short in light fixture

Reply #3 – December 25, 2012, 10:30:40 am

Yahoo Message Number: 135842

First question would be, does the light work? If so, and you want a short and simple, most likely fix, skip to the last paragraph.
From your post I'm guessing that it does, so we'll go from there. There are basically two types of electrical failure modes, shorts and opens. A short being when one wire manages to touch another or ground and an open is when current (electric flow if you will) is interrupted due to a break in a wire or a loose and open connection. Then there are shades of in between . . . that's when a wire is partially open or shorted and this causes what's referred to as a high resistance condition.
The light bulb you are dealing with draws about 1.5 amps and the fuse that protects the lighting circuit is a 20 amp fuse (there are several lights on that circuit). Since the light is working, we are most likely dealing with a high resistance or loose connection. This, believe it or not, can result is minor arcing and a burning smell and heat build-up at the connection due to power being dissipated (voltage drop).
Most likely the problem is the connection at the center of the bulb socket that connects to the solder tab on the base of the bulb. The solder has oxidized or 'flowed' and this is causing a high resistance connection. Remove the bulb and look at the end. If it's corroded, try rubbing it on a rag or paper towel to remove corrosion. You can use a pencil eraser to clean the connection inside the bulb socket if need be. The center soldered connection is essentially just a blob of lead/tin solder that is under considerable spring tension. Over time, heat and vibration, the solder may 'flow' as evidenced by an indentation in the solder - - sometimes this indentation will cause a bad connection too if it's so bad that the insulator at the edge of the solder comes up against the connector in the socket. Fix is to clean the connection, replace the bulb (if the solder tap is really smooched) or to add solder to the tab is you have a soldering iron.

Merry Christmas

bumper
Minden, NV

[Non-text portions of this message have been removed]

Re: Assistance please on electrical short in light fixture

Reply #4 – December 25, 2012, 11:24:59 am

Yahoo Message Number: 135844

Quote

"Do I need to turn off all of the electricty before I take the screws out to inspect the wiring?"

Patricia

Pat

What I expect you will find once you have the fixture dismounted is a pair of wires connected with 'wire nuts'(a plastic cap like device that screws over two wire ends to hold them together).
To avoid getting 'bit' you need to trip the breaker that provides power (12v) to that area of the RV. There most probably will be two or more breakers, one for the front area, and for the middle area and for the rear area.
If the fixture is beyond repair your would remove the wire nuts and connect the wires of the new fixture in place of the old, using the same wire nuts.
However, I see that "Bumper" has provided us with a very detailed intermediate fix. I would follow his instructions before replacing the old fixture.

Let us know how it goes.

Steve S.
Lazy Bones & Jiggs

Re: Assistance please on electrical short in light fixture

Reply #5 – December 25, 2012, 07:38:37 pm

Yahoo Message Number: 135849

"The center soldered connection is essentially just a blob of lead/tin solder that is under considerable spring tension. Over time, heat and vibration, the solder may 'flow'..."
And if it's not making good contact, that little blob can heat up so much that it actually melts and runs--I've seen it happen!
All of Bumper's advice is good. Give it a try and let us know how it works out.

Andy Baird http://www.andybaird.com/travels/

Re: Assistance please on electrical short in light fixture

Reply #6 – December 25, 2012, 07:46:22 pm

Yahoo Message Number: 135850

"you need to trip the breaker that provides power (12v) to that area of the RV. There most probably will be two or more breakers, one for the front area, and for the middle area and for the rear area."
I don't think that's correct for most Lazy Dazes. All the rigs I've seen have circuit breakers for 120 VAC, but fuses for 12 VDC. (There is a master 12V breaker buried in a compartment somewhere, but you can't turn it off--you can only reset it if a major short circuit trips it.)
One 120 VAC breaker handles all outlets, front and rear--they're all on a single 15 A circuit. (The microwave oven and air conditioner are on the other half of the 30A line.)
12 VDC devices are protected by a variety of 12V fuses, which are located in the converter box to the right of the 120 VAC breakers. There's usually a printed label on the inside lid of the box, telling what each fuse controls. For safety, you need to find the fuse that controls that light, and pull it out.
I strongly recommend doing this now, whether or not you intend to work on the light fixture right away, in order to eliminate any chance of fire.

Andy Baird http://www.andybaird.com/travels/

Re: Assistance please on electrical short in light fixture

Reply #7 – December 25, 2012, 10:15:29 pm

Yahoo Message Number: 135851

Quote

"12 VDC devices are protected by a variety of 12V fuses, which are located in the converter box to the right of the 120 VAC breakers.>

Andy Baird

But of course Andy you are, as ever, correct. I was thinking 'breakers' when I should have been thinking 'fuses'.

Perhaps it was too much egg-nog. ;o))

Steve S.
Lazy Bones & Jiggs

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December 24, 2012, 03:46:41 pm

Reply #1 – December 24, 2012, 04:36:33 pm

Reply #2 – December 25, 2012, 10:20:04 am

Reply #3 – December 25, 2012, 10:30:40 am

Reply #4 – December 25, 2012, 11:24:59 am

Reply #5 – December 25, 2012, 07:38:37 pm

Reply #6 – December 25, 2012, 07:46:22 pm

Reply #7 – December 25, 2012, 10:15:29 pm

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