Break/turn signal lights won't work

[aladwig2000]

Hi! Brand new travel trailer owner here. My parents gave me their 2015 Keystone Outback Terrain camper last week.
I drove 900 miles back home over 3 days towing it. On the last day of our trip, some of the lights stopped working when I plugged in my 7-pin connector. The lights on the front of the trailer turn on. The trailer breaks still work. But the lights towards the back, including the break and turn signal lights, don’t work. I jiggled the plug a bit and they started working again, but for only a couple minutes. Once they died a second time, I couldn’t get them back on.
I’ve tested the pins on my truck with a multimeter and they’re all putting out power. I sprayed contact cleaner on them and blew out the trailer plug with compressed air, but the lights still don’t work.
We wired a backup camera to the cables running to the back lights before I started my trip. The camera worked fine until the lights stopped, then it stopped working too. I unwired it, but the wires in the back are still showing little to no power with the multimeter.

I'm attaching a pic of the plug coming from the camper. I'm worried the ground connector on the bottom right of the pic might be busted based on how it looks. But I'm not sure.

I’m at a loss. I just got this thing and I want to take it out camping. I’m no electrician, but is there anything else I can do to try and diagnose/fix this problem?

Thanks for any advice!

[chuckster57]

Welcome to the forum

It’s easy to isolate the problem. Make a short jumper wire and do the following.

Look at your second picture, 12V positive is the 11 o:clock position.

Jumper from 11:00 to the 1:00 and the running lights should work.
Jumper from 11:00 to the 9:00 and the Right turn/brake light should work
Jumper from 11:00 to The 3:00 and the left turn/brake light should work.

If they do the issue is most likely truck/7way socket
If they don’t the issue is in the trailer wiring.

[aladwig2000]

Originally Posted by chuckster57

Welcome to the forum

It’s easy to isolate the problem. Make a short jumper wire and do the following.

Look at your second picture, 12V positive is the 11 o:clock position.

Jumper from 11:00 to the 1:00 and the running lights should work.
Jumper from 11:00 to the 9:00 and the Right turn/brake light should work
Jumper from 11:00 to The 3:00 and the left turn/brake light should work.

If they do the issue is most likely truck/7way socket
If they don’t the issue is in the trailer wiring.

Thanks for the welcome! I'm excited to dive into the camping life. I'll try the jumper wire and let you know what I find out!

[aladwig2000]

I tried the jumper cable like you suggested and the turn signal lights came on. I think my next step is taking out the 7-pin plug on my truck and checking those connections.

[flybouy]

Originally Posted by aladwig2000

I tried the jumper cable like you suggested and the turn signal lights came on. I think my next step is taking out the 7-pin plug on my truck and checking those connections.

If your 7 way socket shows voltage on the contacts and the lights on the camper work when you jumper the 7 way plug on the trailer then the issue has to be where the two components meet. From the picture the trailer plug looks questionable. I would replace it.

[chuckster57]

Originally Posted by aladwig2000

I tried the jumper cable like you suggested and the turn signal lights came on. I think my next step is taking out the 7-pin plug on my truck and checking those connections.

Check the truck fuses first.

[JRTJH]

^^^ There is a 25 amp fuse in the power distribution center on Ford trucks. That fuse box is under the hood. If that fuse blows, the brake/turn signal relays do not get power and all the trailer brake/turn signal bulbs "go dark".

I'd suppose other truck brands have a similar "protective circuit".

If "all the brake/turn signal lights are inop, I'd suspect a fuse before I'd suspect a problelm with the wiring. If only one function on one side is out, suspect a ground or a loose power input wire, but all the lights going out? Probably a fuse.