What grounds the running lights?

[Chuck]

I've gutted the back section of my 'stream, including the univolt/battery, etc, in prep of replacing the floor and adding tanks, etc. Started all this last fall, and had to move the trailer to its winter parking spot (further away from the house, out of the way of snow removal). When I moved it, I just happened to notice that the tail lights/running lights didn't work. (had the umbilical connected...also noticed that the brakes kind of worked, but seemed "weak".) I'm assuming this is because I removed the electrical stuff. But I thought that the running lights were separate from the rest of the trailer's 12v system, mating directly to the vehicle's 12v system.

Anyway, turns out, the winter hasn't been bad here. (record low snow fall) and not all that cold, and I'm thinking that I could still be puttering on a few minor side-projects...the "while I'm in here" type stuff. One of the things on that list is replacing the tail light "cans". Not a major thing, but in the trailer's current state, I won't be able to test connections and such, until I figure out why the existing lights aren't working, and fix that.

(clarification: the running lights/tail lights all worked fine before I gutted the trailer. The one can that never worked was one of the reverse lights, which isn't "necessary" for being on the road, and attempts to remove the existing rusty can from the outside failed, so I figured I'd just do this when I have the interior removed, so that I could reach them from the back....and "while I'm at it"...might as well replace them all while I have the chance).

I would think that the problem is some sort of grounding issue, although, the lights are still attached to the shell, and the shell is still bolted to the chassis...so why wouldn't they still be grounded (?).
maybe the wire that connects to the ground pin on the umbilical was connected through the univolt?

[HowieE]

Generally the body is the ground circuit in an Airstream. That said the connection to the body from a given light is often the problem. Before going too far check for power to the light with a meter grounded to the body. Then check the screws and rivets through the light base to the body. Sometimes the light socket itself will fail due to corrosion.

[Jim & Susan]

What Howie said, plus....

I ran an extra ground wire from the back of the cans to the shell of the camper while I had things apart. One of the cans didn't seem to like the ground the factory provided "all the time". Meaning that the light wanted to work intermittently. Problem was solved by drilling a hole in the can and riveting a direct ground wire over to the shell. Same thing applies to the running lights above the rear window if those lights are troublesome. Simply attach another ground wire to the ground inside light fixture to the shell inside the camper.

Make sense?

Jim

[Chuck]

yes, it makes sense, if I had "a" light that was out, or intermittent. This is *all* of them. all at once. So I'm thinking its a systemic issue. I'll consult the service manual and see if I can figure out where the "-" leg of the umbilical terminates inside the trailer. Its probably dangling there with all the others that I disconnected from the looney-volt. Since there is not complete electrical loop in the trailer, that juice has to find its way back to the truck's system in order to work.

[Jim & Susan]

Ok, I guess I need to read more closely. If you removed he looney-volt completely from the camper AND the fuse panel on front of it, AND disconnected all of the DC wiring from said fuse panel, then most likely you don't have a circuit any longer back to those lights. IIRC, all of the DC circuits pull power from that fuse panel on the front of the Univolt in one form or 'nother (even the brakes, because it needs to use the battery that's connected to the fuse panel in case of emergency need to lock the brakes down).

Hook all that stuff back up to the fuse panel on the Univolt and all should be fine (Univolt off, umbilical plugged into the TV). I mapped out all of the wires to that fuse panel when I had mine apart, to include the items attached to the wires, if you need it.

Jim

[mimiandrews]

Our front running lights failed last December, and we found the wiring for the positive side of the lights had failed. The 18g a wiring used was too small for the five running lights wired to it. Insulation burned as badly as I've ever seen.

It's a miracle that it worked at all, and it did until along about Christmas. Even more a miracle that we didn't have a fire in the front of the trailer from it.

Here's a pic of some of the wiring we pulled out. New wiring is 14ga. New lights are LED's. New circuits have fuses in the trailer instead of depending solely on the fuse in the TV.

[bryanl]

re: " This is *all* of them. all at once. So I'm thinking its a systemic issue."

gutted. means that they were being powered by the tow vehicle?

Check to see if you have a ground lead on the umbilical plug and socket and that the lead is well connected to the trailer and tow vehicle chassis as appropriate.

Sometimes, the ball is used as a ground path and that can be iffy.

[Chuck]

yeah, the whole thing is ripped out...all wires are just swinging in the breeze back there.

those circuits to which you refer are only for the interior fixtures (lights, etc). The running lights don't connect to the univolt; their +12v supply, as well as fuse protection, comes from the tow vehicle's wiring.

Ok, I found in the SM that the ground line from the TV goes to the univolt;
The univolt diagram shows a connection for "negative load". We also see the "+" supply for all the other fixtures in the trailer...but how's that power get back to the univolt/battery?
I can't see it anywhere in the service manual, but from my de-construction pictures, I see a wire coming from the univolt (same color as the neg umbilical line) that is screwed into the interior skin. This has got to mate somehow to the connection at the univolt, and that, I can't see at the moment. I'll investigate tomorrow in the daylight...but that explains how both the umbilical-supplied running lights as well as the univolt-supplied interior lights' power gets back to the univolt...and eventually, back to the tow vehicle's ground.

[pgr32e]

Tail/running lights and brakes are run from the TV. The only time the brakes are run from the trailer is when the disconnect switch is pulled. It sounds like you have a ground problem between the TV and trailer.....Phil.

[Chuck]

So I did some poking around inside the trailer. (I was only referring to pictures, yesterday).
Turns out, there are 2 white heavy gauge wires in the bundle that disappears up behind the end cap; the one that attached to the univolt, and the other connected directly to the interior skin.
I connected up the truck to the umbilical, and found that the large blue wire was showing 13.8 volts (truck was running) when I probed it and either of the white wires. Then I also found that touching metal on the trailer w/ the "-" probe also showed the completed circuit, too. {puzzled}

So I went out and turned on the truck's headlights, and wouldn'tcha know, the running lights on the trailer come on.
Umbilical must have just been a little loose when I moved the trailer.

I'm still curious about that second white wire, though.
And also, while the running lights came on, they were dim...like you might see when there is a "bad ground". Tail lights looked normal, though...but those are pretty bright bulbs.
The brake controller has a light on it that shines when there is a completed circuit, and that was lit...and I remember when I moved the trailer, the brakes worked, but they were weak. had to use the thumb switch and press it nearly all the way before I felt anything, and the brakes wouldn't "grab" me to a sudden stop like they would normally.
Anyway...I'll be able to install new tail lights and test them ok without completely re-connecting all of the electrical system.