Trailer Lights Not Working

[Wyokirk]

It's an electrical day.

We brought the trailer (2008 31 foot Classic) home from storage last Friday. All exterior trailer lights were working: running lights, turn signals, brake lights and tail lights.

Today, I was hooking up our rear facing camera - which is powered off the running light circuit - and the lights are not working.

We have power from the tow vehicle - checked with a multi-meter.

Cleaned the 7 way plug - both sides and added conductive grease. No change.

I checked the two fuses I could find under the couch - they were OK.

We had lithium batteries, new converter, inverter and solar added last fall, so the 12 volt breakers that were located under the couch on the left side have been moved - somewhere. Is there a breaker for the exterior lights? The only way to further investigate the location of the breakers will be to move the couch - which we have done several times.

I have found two ground wires under the A-frame - but both set screws are corroded to the point they won't turn. I have applied WD-40 - still won't move.

Any thoughts, comments, recommendations are appreciated. Thanks in advance.

[BikeCamper]

Stuff like this can be very frustrating.

I would focus on getting those ground wires cleaned up first. A faulty ground can be a source of this kind of problem. WD-40 can help to keep connections in good shape, but is not the best for trying to clean-up and break free rusted connections. I would try something like PB Blaster or similar, break the set screws free, then go to town cleaning the wires with a wire brush.

[Wyokirk]

Thanks for the reply. On my way to autozone for PB Blaster.

[Tim A.]

Do you happen to have a new tow vehicle? If so, you might have a problem like we had. New tow vehicle and marker lights sometimes went on and sometimes did not. Turned out the incandescent bulbs in the marker lights had too much resistance for the trailer sensor system in the new tow vehicle. Changed out the bulbs to LED and all has been well.

Tim

[richard5933]

If your grounding screws are that rusted, abandon them and use new. Cut off the ends, strip to bare/clean copper, and use new fittings. Here's a photo of what I did. In addition, I have a standard copper grounding lug on the rear of the trailer to fasten the grounding wire from the 120v breaker pane.

[Wyokirk]

I bought the PB Blaster last evening and "blasted" to bolts/set screws where the ground wires attach to the frame. But, i used my multi-meter this AM on the OHM setting to check the resistance (continuity) between the bare ground wires and the frame. Filed some paint off of a corner. I had zero resistance between each wire and the frame. I believe this indicates the system is grounded - correct.

We do not have a new tow vehicle and the lights worked (we always check after hooking up) when we towed the trailer from storage to our house - about 7 miles.

Current plan is to lift the couch to see if I can find the 12 volt breakers.

[MaineStreamer]

Your tow vehicle headlights must be turned on in order for power to go to the trailer.

[NeahBay]

Wyokirk,

You mentioned hooking up your review camera, which I’m assuming after that the lights went out. If so, what was involved in “hooking up” the camera? Did you simply plug it in, or actually cut wires to install?

As in most situations like this, back track to the point when the lights last worked to see if you find the problem. Put things back the way they were as much as possible.

Also, are all the wire connections tight from the 7-way, especially into the 12vdc panel? Something came loose (I state the obvious), during camera install and/or 7-way cleaning, or now both (double whammy).

“Fun” problem, IF you have the time (for me at least), not so much otherwise. On the bright side, you’ll get even more familiar with your wiring system, which is a good thing.

Bob

[Hikingsolo]

My most recent problem with trailer lighst traced back to a broken connection inside the 7 way.

New TV 7 way fixed it. And $230.

[Wyokirk]

Thank you for all the replies.

Our rear facing camera gets its power from the running lights - was installed in April 2017. "Hooking it up" refers to installing the monitor back into the cab of the pickup. No new wires. When towing the trailer, the lights are always on to power the camera.

We lifted the couch so we had access to the electrical. Checked the 12 volt breakers - they are OK. Connections are tight.

I checked a couple of the running light bulbs to see if they were burned out - they are fine.

Electrician friend came over yesterday PM and we spent 2 hours investigating. Replaced the 7 way plug on the trailer side. We have continuity from the trailer 7 way plug to the 12 connections inside the trailer. We also replace the trailer 7 way plug. Started to rain so we stopped to spend the night contemplating the problem.

[BikeCamper]

I take it you have power on the tow-vehicle side of the 7-way plug? And have checked all fuses on the TV?

[Wyokirk]

We have power at the 7-way plug. We have not checked fuses.

And, as expected, no brakes either.

[richard5933]

Originally Posted by Wyokirk

We have power at the 7-way plug. We have not checked fuses.

And, as expected, no brakes either.

Almost sounds like your 7-wire cable got pinched, stretched, or otherwise damaged. This, or the junction point for the 7-wire cable to your trailer's harness was somehow disturbed. Mine sits behind the couch.

[BGClassic]

By chance, do you have an extension cable on your 7-pin tow cable? I just experienced this with our Classic. We have a 24 inch extension, and I lost running lights. Had corrosion in the socket of the extension cable.

[SnowWanderer]

My 2019 RAM Limited has a four position headlight switch. My trailer lights work when the parking lights are on, and when the headlights are on, BUT when I turn the headlight switch to the fourth setting... the auto headlight setting, the trailer lights do not work.

[Wyokirk]

Not posted in a couple of days so will provide updates.

I have checked all the fuses in the truck. OK
We do not have an extension cable.
We have a Ford F250, with a 4 position switch. Lights don't work in the 4th position - always run in the 3rd position.

Friday PM, out of all other options - I had one last thing to try. I hitched up the pickup to the trailer just like we would on any trip - and everything worked - running lights, signal lights, brakes and the DC-DC charger turned on in the trailer.

Theory is that hooking up closed the ground connection between the truck and trailer. I don't recall ever hooking up the 7 pin connector to the trailer with this truck and not being hitched up. I know that I did it with the previous truck (a 2021 F250) to charge the trailer batteries in a campsite with out 30AMP.

I have checked the ground on the pickup - ground pin in the 7 pin connector has continuity to the license plate holder.

Will check grounds in trailer next.

I have a call with an Airstream dealer on Monday with the tech who did some electrical upgrades last fall to discuss issues.

I have an appointment with a Ford dealer in a couple of weeks to check electrical. They did some work on part of the electrical system in March (drivers side heated seat).

[richard5933]

Is your DC-to-DC charger the kind that isolates the ground connection from trailer from the TV?

[Wyokirk]

Richard - yes it does. Orion-Tr Smart DC-DC Charger Isolated. The charger has 4 wires going to it, 2 white and 2 black.

[richard5933]

Originally Posted by Wyokirk

Richard - yes it does. Orion-Tr Smart DC-DC Charger Isolated. The charger has 4 wires going to it, 2 white and 2 black.

The solution might be as simple as putting a jumper on the Orion to bridge the ground connections.

[Wyokirk]

While this is not directly related to the original thread, it may all be connected. I hitched up to the trailer yesterday (only way to make the lights work) to run some tests on the DC-DC charger. I wanted to see how much power is provided by the pickup and DC-DC charger. I first ran the batteries down to about 80% capacity (three 100 Ah lithium) and then covered the solar panels with some beach towels - yesterday PM was cloudy. With the pickup running and the DC-DC charger on, there was +0.15A at the battery monitor. With the pickup running and the DC-DC charger off, the battery monitor shows +0.18A - must be some light coming through the towels.
I don't believe the DC-DC charger is working - at least not correctly. Is it possible that with the DC-DC charger on, power is feeding back to the pickup?