12V circuit oddity

[gkainz]

I have a 2010 Keystone Laredo 245RL with a recently discovered electrical oddity or two or three ...

I have 2 overhead lights in the slide out. One would assume they are on the same circuit. Circuit 15 in the DC panel is marked "Slide Out" and is an orange/white wire.

Both light fixtures have LED bulbs in them, and now Light 1 is very dim, while Light 2 illuminates normally. (Edit: Tested ALL LEDs in light 1 and light 2, as well as replaced them temporarily with incandescent original bulbs - this is not a bulb problem, I'm quite sure).

The dim fixture (light 1) (orange/white wire) reads 7.8VDC at the wire connector at the fixture connection when any load is on the circuit. Meaning 1,2, or 3 bulbs in the fixture and switch on reads 7.8VDC at the fixture.

With ALL bulbs removed, the fixture reads 13.8VDC when switched on.

With bulbs installed, 7.8VDC at the switch, bulbs removed (no load), 13.8VDC at the switch.

The orange/white wire reads 13.8VDC at the DC panel regardless of load or no load.

Removing fuse 15 disables the fixture (light 1 ONLY).

Light 2 works normally ... except ... it's not on circuit 15.

Pulling the fixture down exposes a green/white wire.

Circuit 4, Kitchen is the green/white wire at the DC panel. Pulling fuse 4 DOES NOT disable Light 2 - it continues to burn ... oops, bad choice of words ... "stays energized".

Thru trial and error, I discovered pulling fuse 2, marked Furnace, connected to yellow/white wire, disables Light 2. The Fridge is also on this circuit, altho not marked as such.

So, anyone able to put all those clues together and make some guesses as what to check where?

The real oddity is Light 1 worked last season and nothing was changed over the winter.

Perhaps somewhere the green/white to Light 2 is broken/cut between DC panel and before slideout, and then connected to (intentionally/accidentally or via wire damage?) yellow/white wire near or around furnace or fridge?

Bad + or - connection on orange/white wire on the way to slide out Light 1?

and finally, to circle bad to my original premise, one would assume both light 1 and light 2 would be on the same (slide out) circuit ...

[BurbMan]

I can tell you that I have 4 light fixtures in my slide and they are all fed by the same circuit. True that there are multiple lighting circuits so a blown fuse doesn't leave you in the dark, but typically only one wire runs to the slide.

Before you drop the belly, extend the slide and look under the floor. On mine there is a flexible plastic carrier that holds the single 120v stranded cord and single 12v pair in two separate 1/2" split loom conduits. These are zip tied to the plastic carrier that manages the movement of the wires as the slide extends and retracts. I would look there first, and see what you can find.

Of course yours may be wired differently than mine but the way the industry works, it seems unlikely that they ran two 12v circuits to the slide lighting. But the wire carrier setup is pretty common to all slide outs. How many 12v wires will at least tell you how many circuits service the slide.

If I had to take a SWAG, I would say that fixture #1 is in reality dead, but picking up phantom voltage somewhere so that you get a 13.6 reading with no load, but the slightest load (even from an LED) makes it disappear.

If you can't find the problem, Plan B would be to disconnect the wires from fixture #1 and cap them in the ceiling (allowed with low voltage, but not with 120v) then fish a new wire thru the ceiling from fixture #2 to power fixture #1. Then they will both be on the same circuit anyways. :B

[gkainz]

Good ideas and thoughts all ... more things to check.

I didn't have long enough meter leads or an extension to cross between the fixtures to use the ground on the good one, but will tonight.

Same behavior with slide in, out and spots in-between - I examined the wire bundle under the slide where I could see it, and there are no pinches, kinks, twists, abrasions or cuts anywhere visible. Tonight I will probably drop the coroplast belly and chase the wires further.

The voltage drop regardless of the size of the load really doesn't make sense - Ohms Law says it shouldn't happen that way.

I did eliminate the switch by unplugging and jumping the wires at the switch. No change in behavior.

Furnace and fridge operate normally. Just got home from our first outing of the season and no issues with either.

I did examine, remove and re-seat the wires in the lugs on the DC distribution board. All are clean, no loose strands, stripped properly and lugs were snug.

I may have to pull the fuse panel out to find the grounds. They're apparently hidden somewhere behind the panel (or hiding in plain sight over on the A/C half of the panel ... but I didn't see them last night.

So, I really do have 2 separate issues:

First, the low voltage to light fixture (light 1) with any load, properly on Circuit 15, orange/white wire all the way from fuse panel to switch to light. Perhaps a bad light fixture? I didn't cut away the crimp wire nut and completely remove the fixture, just probed into the back of the wire nuts.

Second, (multi-part) the normal light fixture (light 2) "should" be on Circuit 15 (just because my OCD says it's in the slide out and should be on the slide out circuit), and they wouldn't split the circuit for load, as (2) 3 bulb fixtures would not overload a 15 amp circuit. No reason to split those into two circuits.
Then, the oddity of light 2 connected to red/white wire, and red/white wire at the panel is obviously not continuous to the fixture, and apparently red/white fixture segment is fed by the yellow/white from somewhere downstream of the panel.

[Golden_HVAC]

I would also be looking at where the wires to the slide out flex often.

You might try running a new ground wire between light #1 and #2, to see if that might be the problem. Make sure you are attaching ground to ground, or fuse #15 will blow in addition to the fuse that runs the other light.

Normally they run multible fuses for the lights, so that if one blows, you will still have lights in part of the RV.

Also the slide out wiring is probably connected in the basement, while other roof mounted lights are connected overhead.

Chances are that where the wires flex, there is a loose connection, perhaps a loose wire nut, or a flexible wire that has flexed one to many times, and nearly all the copper wire in it is broken, leaving just one strand to carry the 7.6 volts under load.

However I am also wondering why when you are running a 0.02 amp LED light and a 1.2 amp normal bulb, you might still get 7.6 volts to the open side of that light. LED's normally use well under 0.5 amps, and normally there has to be a 'huge' voltage loss or very weak connection to cause the voltage to drop at all!

Fred.

[newman_fulltime]

my guess knowing keystone the oversized wire nut at the furnace (you will see) the wire going to the slide has been pulled out some so when no load it reads volatage when loaded votage drops like a bad battery on cold cranking amps

[Hiking_Hunter]

Bad switch? Try turning light 1's switch on, then short between the terminals on the switch to see if it gets brighter (proving a voltage drop across the switch).

[grizzzman]

A does the furnace and fridge work correctly?
B it is possible that light one is tied to the heater/fridge
C I would look REAL close at the wiring that flexes at the point were it bends durring slide opperation

[MEXICOWANDERER]

SLIDE OUT means something...

It means wires for lighting slide in and out. Both switched and negative sides.

Test weak fixture positive with normal fixture negative. Whaddya got?

Then weak fixture negative with normal fixture positive. What's up Doc?

Might as well know which circuit is high resistance.

Then extend the slideout and start looking fir pinched wire harness.

[JamesJudasPries]

I'm sure you checked all terminals for tightness (fuseboard positive and ground) Maybe one of the wires for the light was improperly stripped somewhere, you know, accidentally stripped using a smaller gauge than the wire size, losing strands and ampacity, causing that nasty voltage drop. See if you cant find somewhere in the circuit where someone decided to use the #18 wire stripper graduation instead of whatever it actually is.

[tenbear]

Good problem.

Do both lights use the same ground?

Can you find a good ground and check the voltages on the wires to light 1 using your good ground rather than the voltage between the 2 wires going to light 1? This should identify whether it is a ground problem or a +12v problem.

I find it odd that the voltage is the same whether you have 1, 2 or 3 bulbs in the light, or incandescent or LED bulbs.