Bad Ground wire taillights Dim

[angler]

So I'm doing troubleshooting for my dim tail lights. My meter indicates about 10.5 volts at the taillights. I think I know where the ground wire is, but not the color I expected at the assembly. only white wire I have is going to the backup lights. Thought I'd have more. Black and dark blue wires.
Inside I'm reading 12 volts.
Anyway does this look like the ground for the taillights its located on the hitch so I'm not sure if its for the hitch wiring or the coach. Probably would be difficult to trace it back. Just wondering for people who had to fix ground wires if this is what it looks like.

[enblethen]

Some tailight converters require a ground.

[angler]

Thanks for everyone's help. (used the self tapping screw and extension cord ideas)
That was the ground for the taillights or at least something that affected the voltage of the lights. I am at almost 11.5 volts now. Even when I run the ground right off the battery. I get the same voltage. Looks like a controller unit for the 7 pin connector was added at one time which may be the problem. Again thanks for the help.

[grumpy3b]

DrewE wrote:
If the wire is connected to the frame, it's a ground. The color is meaningless at that point. More generally, expecting a consistent color scheme on RV wiring is quite optimistic, and even more so if people have had to make repairs or additions or changes over time.

That's so right. On mine I've found 2-3 wire color changes on the same run/circuit. Can be really tedious to sleuth out. Great tip!

[enblethen]

Self taping screws can be used for connection but should have at least three threads into the host material.

[Wild_Bill_888]

Didn't have 40 feet or so of wire either to connect to the battery.

Use a long 120V extension cord as a jumper. Connect prongs to neg battery post, insert neg meter probe into female slot of cord. Check voltage on both sides of the bulb to see which leg has most of the voltage drop.

To check a ground point use a sharp needle to puncture the ground wire insulation near the ground point and measure voltage to bat ground with current flowing. Also measure frame voltage to bat ground with current flowing.

If the voltage drop is distributed over very long wire runs switch to leds to reduce current and voltage loss. Also works for dim halogen headlights.

Looks like water stands in that area.

Right, seal entry or drill a drain hole.

[DrewE]

If the wire is connected to the frame, it's a ground. The color is meaningless at that point. More generally, expecting a consistent color scheme on RV wiring is quite optimistic, and even more so if people have had to make repairs or additions or changes over time.

[angler]

Do self drilling screws go through plate steel?

[BB_TX]

Looks like water stands in that area. When redoing that I would move it higher and on a vertical surface. You can use a self drilling screw to make it easier.

[angler]

not sure about the black wire. Noticed it too, but didn't see a black wire anywhere down there. I think black is hot on a rv...maybe? The wiring on these things don't seem to make any sense to me, but I'm not an expert on wiring.

[enblethen]

Looks like the black one is completely separated. Note the green on the end which indicates it is copper.
Yes, it could be ground for trailer connector and possibly the lights.

[angler]

I measured across the bulb. Tried to run a find a spot on the frame for a good ground, but didn't have anything with me to get the paint/rust off. Didn't have 40 feet or so of wire either to connect to the battery.
This bolt probably won't turn off anyway. Have to cut and drill it out I imagine. Maybe before I do that I'll cut the insulation back on the wires a little and wrap a wire around it and bring it to the front for a good ground and see if it makes a difference before I start cutting bolts. Leaving town in a couple weeks and don't want to make too many fixes before I hit the road:) Thank you for your help in identifying the ground for me.

[BB_TX]

Are you measuring the 10.5 volts across the back of the bulb socket? I would use the meter ground wire direct to the frame to get a good ground and make sure you have a full 12 volts to the bulb.

But the connection definitely needs to be cleaned up no matter what it is for.

[MountainAir05]

Its a ground for something. You will found many grounds on a rv. Looks bad.