What to check next <trailer lights not working>

[Freezer41]

Was planning on my first trip to the lake for the year but my lights are messed up. First thing noticed was the reverse lockout was not disengaging. I cleaned off all the contacts as best to could.

Running lights work.
At some point while cleaning the contacts the left turn signal started working.
I though I had traced it back to the connection near the light (pictured).

With running lights on, jumpered to green wire contact and light came on bright. I can rule out the lamp and lamp side connector. Right?

Multimeter shows 9v at aft harness connector green wire when brake depressed.

I'm stumped. Someone said check the ground. Where is is on this trailer?

Any help or tips would be appreciated. Now my car battery is dead from all the testing LOL whoops

 

[biglar155]

9 volts at the aft connector could indicate either a high-resistance short to ground somewhere (enough to bleed off a little current and drop your voltage but not enough to blow the fuse) or possibly a bad connection that is has enough resistance to provide a couple of volts of drop.

The ground (connection to the negative post on the battery) is the white wire. Normally this is connected to the trailer with a screw and the trailer frame becomes the ground. Based on your picture though, it looks like you have a white wire running the whole way back to the light fixture so in theory the frame ground wouldn't affect the lights - assuming it's running all the way to the vehicle and not just hooked to the trailer frame somewhere I can't see from here.

Still, the fact that your reverse lockout isn't working points to something common - which could be the ground but I'd expect the other lights to not be working correctly either.

Well, start by making sure you have a good ground. As I said, normally the trailer is the ground and you need a good metal-on-metal connection to the white wire on the harness and back to the ground pin on the truck connector.

Take a look at the white wire on the harness end. Does it connect to the trailer with an eyelet and screw somewhere? Is that connection good or is it all rusted up? If so, clean her up. Check your swing-away connection. If it's rusting up in the hinge, it could be losing the ground there.

Absolute worst case scenario: Disconnect EVERY light (don't forget the side-markers) and check resistance between the wires (they should all read open). Then grab a piece of spare wire, run it on the ground along side the trailer and use it as an "extender" for your mulit-meter to test every wire for continuity.

Current just needs a complete path to follow. It should be easy but sometimes it really isn't.

 

[jdonalds]

It took me many frustrating years to discover Marine Electronics Grease. Prior to that I would clean contacts physically, spray electrical cleaner in the contacts, sand them, or whatever but I always had problems with the contact so my trailer lights often did not fully function.

Of course any bad grounds will cause havoc too.

Once I cleaned the contacts and applied this grease https://www.amazon.com/CRC-06106-Marine-Electronics-Grease/dp/B001HXI8C6/ref=sr_1_17?ie=UTF8&qid=1495427625&sr=8-17&keywords=electrical+contact+grease

my trailer contact problems disappeared. I haven't had to do anything to the wires in over two years.

​

There are other brands. This is just the one I use.

 

[dan144k]

Trailer light problems are frequently the ground connection.

 

[KXCam22]

I got so tired of mfi lite probs that i ran a dedicated ground wire down each side. Now no issues in years. Plus use led lites. It is worth doing the revamp to then never have probs again. Cam.

 

[biglar155]

I got so tired of mfi lite probs that i ran a dedicated ground wire down each side. Now no issues in years. Plus use led lites. It is worth doing the revamp to then never have probs again. Cam.

Which fixtures did you use? I bought a set at fleet farm last year but the bolt spacing wasn't right so I returned them. Been browsing for something with 4" spacing on the bolts but a lot of times they don't specify that in the description.

 

[Zonie]

As others have stated, check the ground first. Sometimes if the ground wire has a bad connection or is not connected at all, the trailer will ground through the hitch. This can cause intermittent or high resistance ground problems. You can easily test this by unhooking the trailer from the tow vehicle and then plug the wiring harness in. If the lights don't work at all, you know the ground is open. Also I would check to make sure everything on the vehicle is working correctly. Attach your DVOM or test light to the truck and make sure you are getting a good signal for each of the outputs, running lights, L&R brake/turn signal, and reverse. You can also check the ground on the vehicle by grounding your DVOM to the vehicle and checking for continuity through the ground wire on the plug. Once you verify everything on the vehicle is working properly you can start troubleshooting the trailer lights.

 

[Zonie]

Which fixtures did you use? I bought a set at fleet farm last year but the bolt spacing wasn't right so I returned them. Been browsing for something with 4" spacing on the bolts but a lot of times they don't specify that in the description.

I got all my LED lights from ETrailer. They were an exact fit and easy to install. At the same time I added a set of LED backup lights to the rear crossmember. I rarely launch at night but it's often dark when I get home and its nice to be able to see what's behind the trailer.

https://www.amazon.com/gp/product/B00RA4HOPI/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

 

[biglar155]

I got all my LED lights from ETrailer. They were an exact fit and easy to install. At the same time I added a set of LED backup lights to the rear crossmember. I rarely launch at night but it's often dark when I get home and its nice to be able to see what's behind the trailer.

https://www.amazon.com/gp/product/B00RA4HOPI/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

Oooh! I like that!

Dang it @Zonie! You've only posted 34 messages and you're already costing me money.

You sure catch on quick!

 

[KXCam22]

I used some grote ones i got cheap. Had to drill one new mount hole. Cam.

 

[blacksapphirez]

try to pull the harness from the rear where it splits.

I've had one of the split plug melted from a short... i had to repair that to get the lights working again.