Grounding Problem?

[Old Stogie]

I'm having the devil's time trying to get the trailer lights working - turn signals, stop light, running lights, etc. I have power to the end of the umbilical, but no lights. Can you give me some troubleshooting tips, suggestions to try? I've heard it could be a grounding issue, but...BTW, I'm pretty stupid on electricity, but can follow directions well. TIA

[A W Warn]

Welcome to the forum! My first Airstream trailer was a 73 Excella 31'.

Each light fixture should be individually grounded to the skin. The ground wire from the umbilical should be ground to the frame, and therefor the aluminum skin. Also, the ground between the trailer and tow vehicle must be continuious, so check continuity of ground between the two.

It can be confusing when looking at the running lights, since there sometimes are two wires (especially the running lights). Both of the wires, if they are the same color, are hot (+). Looking at the bulb housing (if they are original) you will see that at one of the fastener holes also has a metal ring that acts as the ground to skin that is continuous to the bulb housing. The contacting surfaces corrode from moisture and also from being dissimilar metal. That is a normal maintenance issue.

Also, if lights have been replaced with a fixture that does have a ground wire, then that wire has to be grounded at the fixture. A screw or a pop rivet is what I have seen in this case, attaching a green or white wire that is connected to the bulb base to the skin.

ps:
The color coding for the wires is not the same standard as today's. Check each wire individually for function. Do you have a manual? I'll find one for you. Be back soon....

[uncle_bob]

Hi

Since most trailers have been converted over to a 7 pin connector, I'm going to assume that is what you have. It really does not matter, but it is an assumption on my part.

Power comes from your TV on a specific wire for your lights. There is another wire for each turn signal. Another wire goes to the brake lights. Yet another wire goes to the brakes on the trailer (if you have electric brakes).

Past that bunch of wires, there are two more. One is a ground - it acts as the return for all the stuff above. Another wire can supply power to the trailer for things like charging the battery.

When you want to signal a turn, your TV puts 12V on one of the wires on the 7 pin. That voltage goes into the trailer and off to the various signaling lights. The other side of all the lights gets run back to the ground wire on the 7 pin. That wire hooks into the negative on the TV. Break that circuit anywhere along the way and ... no lights.

Often the negative side of a 12V system in a car or truck goes through the chassis. In some cases the same is true on an RV. With a 7 pin involved, the chassis would need to be hooked to the ground on the 7 pin.

How to proceed:

Grab your multimeter (if you don't have one, get one) and find a convenient light.(brake is probably the best)

Pop off the cover.

Probe across the bulb socket as a helper does whatever it takes to turn on the light. One would guess you will not see 12V (if you do, the bulb needs to be replaced ....).

Next do the same thing, but check each side of the socket to chassis. You may or may not see 12V. (if you do, the ground on the socket has issues)

If there's still no fun, go back to the 7 pin out of the TV and see if you have voltage to ground on it. If not, you have a truck problem.

Now plug the 7 pin back in and measure chassis to chassis between the TV and the TT. If you see 12V then, the ground on the 7 pin is not hooked to the chassis of the trailer.

If that still has not fixed it, come on back and we'll dig still further.

Diagrams for just about any connector you are likely to have:

https://www.etrailer.com/faq-wiring.aspx

Bob

[A W Warn]

Hope this helps>
https://www.airstream.com/wp-content...xcella-500.pdf

[TG Twinkie]

As a quick note. Unless your trailer has separate turn signals and brake lights the brake lights and turn signals use the same wires.
I would leave the TV out of the testing procedures and use a battery charger as a power source to check the lights out.
Connect the black lead of the charger to a clean spot on the frame. Use the red lead to power each circuit.
Once all circuits are working and the 7 pin plug is wired to match the TV. You should be in business.

[J. Morgan]

Trailer wiring is overall fairly easy to troubleshoot with a test light and a systematic approach.

Start at the seven way plug at the front of the trailer with the running lights and four ways turned on and work your way back while grounding the test light to the trailer. (That checks your trailer ground at the same time)

If you have power at a particular spot everything toward the front is good and the problem is behind you. If you don’t have power at a particular spot the problem is toward the front of the trailer.

That said, 12 v trailer light issues are mostly always at the seven way plug or at or near the lights. The wire runs in between are almost never the problem. There is a plastic box under the couch where the umbilical enters the trailer that serves as a junction box. My bet would be that over the decades there has been a lot of “wire fixin’ “ going on in that box. I put the odds at 2 to 1 that you find your issues right there.

Test light, test light, test light.... if you don’t have a test light get a test light....

Edit- it wouldn’t surprise me that on a 73 trailer that all of the bulb sockets are so corroded that not a single bulb will burn.

[uncle_bob]

Originally Posted by TG Twinkie

As a quick note. Unless your trailer has separate turn signals and brake lights the brake lights and turn signals use the same wires.
I would leave the TV out of the testing procedures and use a battery charger as a power source to check the lights out.
Connect the black lead of the charger to a clean spot on the frame. Use the red lead to power each circuit.
Once all circuits are working and the 7 pin plug is wired to match the TV. You should be in business.

Hi

If the 7 pin ground wire is no longer connected to the trailer chassis (which is a pretty good bet in this case) you will not catch that by hooking directly to the trailer chassis.

Bob

[TG Twinkie]

If the battery charger connected to the frame gets you to where the lights work that's a good sign.
If the lights go out when you disconnect the black wire from the frame and do not come back on when you connect the charger to the white common/ground wire. You have a problem with the common/ground side.
Look for the place on the frame where the common/ground is connected. Disconnect it and clean the frame and the point on the wire which makes contact with the frame.

[mythbuster88]

Another unresolved thread ;(

[uncle_bob]

Originally Posted by mythbuster88

Another unresolved thread ;(

Hi

Not uncommon - poster pops up with a question and then more or less vanishes. Very common here and on just about every forum I've ever been part of. Coming back to say that indeed the bulbs were all fried or that the 7 pin was not plugged all the way in ... not easy for a lot of people .... The obvious value is that the next guy along would read that as the solution and maybe get his fixed a lot quicker.

Bob