Light fixture voltage differences - normal or sign of problem?

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Phil Hyde

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In the process of changing out our interior light bulbs to LED's, I have been measuring the voltage at each fixture.  After experiencing a melted fixture cover in an outside storage bay, and an interior bulb that looks like this (attachment), it was suggested that I measure the voltage.

The voltages were different enough to cause me alarm.  They varied from 11.9 to 13.5.  Is this range normal, or does it indicate a serious problem?
 

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Phil Hyde

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Here is the cover that melted.  Voltage here is 13.8
 

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BobNSam

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The normal range of 12VDC is usually defined as 8VDC to 14.5VDC so your ranges are acceptable for compatibility of devices for design. During operating load changes and the type of battery charger installed the voltage can vary within this range and still be good.
The overheated lens is normally caused by the incorrect bulb being installed.
 

Mopar1973Man

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Ok... If you voltage testing (with the battery running) all at the same time and seeing lower voltages at one fixture vs. another one then I would say it a weak connection in the wiring or fixture that is possible.

 

Foto-n-T

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DC (Direct Current) doesn't like to travel, it also doesn't like to travel through stranded wire, voltage losses can be significant.  In a perfect world DC would be wired with solid wire but it's not practical and it definitely wouldn't be cheap.  Your voltage issues more than likely stem from the fact that the manufacturers love to use crimp connectors, the connectors themselves are of course not made of copper and as such can suffer from dis-similar metal corrosion which will impede voltage.

I'm going to guess that it's a combination of both issues that drops your voltage.  The high reading that you've got is well within range, it's the low voltage readings that could mean you've got some resistance that is getting in the way but it's still not excessive.  If you've got dimming issues with your incandescent bulbs then the installation of the LED's should eliminate the problem.
 

Phil Hyde

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OK, well that's good to know.  I was concerned that there might be something wrong with the converter.

Per your comment about voltage loss, it did seem like the voltages were high closer to the center of the RV (where the converter is) and low the farther away I was.
 

Alfa38User

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If you converter was charging while you were plugged in, a very likely event, then that explains the 13.5 Volts. The 11.9V might indicate a poor connection somewhere along the line but....
 

John From Detroit

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Regarding the comment on DC current not liking to travel epically over stranded wire....

Actually AC or DC, that is a true statement,  When you get high enough in frequency Stranded MIGHT< and I stress MIGHT be better but, the fact is that at 60 HZ, might as well be DC for all practical purposes.

The reason for the varying voltages is one of two things.

1: Flakey meter (hey it happens) NOTE: this also includes poor contact between meter leads and wires under test.

2: Length of wire run if the socket is under load.. This is the biggie here I suspect.  For example.. I have a very heavy power sucker (Kenwood TS-2000, sucks up to around 20 amps) the run from the fuse box to the radio is less than six feet.  (The wires to the fuse box are.. Well let's just say they are more than up to 20 amp... Times FOUR).

But to get to say the front light Well that run is close to 50 feet, and each lamp (1156) Draws about 2 amps.. I"m switching to1041's (1.5 amps) and may even go to 1003's  in those sockets (around 1 amp)

NOTE: amprage is seriously rounded.
 

Ernie n Tara

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Hi,
We had similar problems with lenses melting and about eight months ago I replaced all fixtures with LED fixtures. Problem solved! We have really enjoyed the whiter light from the LED's and have not seen any flickering or changes in light level. I'd note that we've been in the MH for seven of those months.
Ernie
 

Foto-n-T

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I too am a BIG fan of LED's but mainly because they eliminate the need for me to pay too much attention to lights when we're boondocked.  The downside of course is that the little buggers are wickedly expensive, so much so that I still haven't converted the entire rig over, just our primary lights like kitchen, dinnette, bed & bath.  Incidently, I did have one them fail a year or so ago but I will eventually change all of our lights over one of these days.

I got educated about stranded wire and DC many years ago with a 1968 Cessna Cardinal that I owned, the battery was behind the baggage area in the rear of the plane.  The extreme run of wire led to starting problems if the battery wasn't absolutely 100% as well as all the connections perfect.  The only plus on that arrangement was that it was easy to get jumper cables on it without putting yourself in close proximity to that big fan on the front but AAA still refused to jump me, go figure.
 

Kamper Dave

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Phil, Please checkout this old post.
A similar problem but caused by the LED arrays.

http://www.rvforum.net/SMF_forum/index.php?topic=54075.msg499549#msg499549

Good luck.
Kamper Dave
 
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