Right turn signal and right brake light not working

[gary s swenson]

2017 3721 legacy I have verified that the 7 pin on the truck is working fine by connecting it to my utility trailer that has a 7 pin plug and it works fine. I have removed the lights and made sure there are no loose connections. The bulb on the right was bad and I replaced it, but still does not work. I am open to suggestions on how to start troubleshooting. Thanks Gary

[scottz]

Gary, first make sure the right brake/turn is working on your truck. Then, use a volt meter at the trailer bulb socket, verify you have voltage with trailer hooked up and brakes on. If you have voltage it is the bulb. No voltage, you have a problem with your 7-pin plug; clean it real good & use some WD-40. Other reason for no voltage, an open between the 7 pin and the bulb socket.

Likely places for an open: the splice where the wiring connects to the bulb socket or the junction box on your pin box where the truck cord is connected to trailer wiring. Between those two places should be nothing but wire.

[Daryles]

Did you check the wiring junction behind the left light?

[rohrmann]

Make sure the ground wire to the right side fixture is intact. Even if you have the hot wires getting power to the bulbs, without the ground connected, they won't work.

[BB_TX]

I am with the guys above. Use the voltmeter to determine whether you have voltage at the socket or not. (Touch the meter ground wire to trailer frame rather than the ground connection on the socket.) That tells which direction to look next.

If voltage at the socket, but lights do not work, then it is most likely a ground connection problem of the light fixture ground wire. Although that ground wire should be common for the taillight for that fixture also. Does the taillight work?

If no voltage at the socket, even when using frame as ground reference, then there is a connection problem between the socket and the 7 pin connector, possibly in the junction box under the pin box. Possibly in the wire connection where the fixture wire connects to the wire from the 7 pin harness.

[gary s swenson]

I have verified that the ground wire is good, checked for any loose connections in the junction box on the pin box. Also checked for any loose conditions behind the left light. Even swapped the bulb. Still no right hand turn light.

[BB_TX]

Check for voltage to the lamp socket. If no voltage there, find where the light fixture green wire pig tail (right stop/turn) wire connects to the trailer wiring. Check for voltage at that wire connection.

If no voltage there, then open the junction box on the pin box and check for voltage on the green wire there. Just going to be a matter of finding where there is voltage and where there is not.

You can put a temporary jumper wire between pins 4 and 6 on your trailer cord connector to put a constant +12 volts on the green wire.

[gary s swenson]

Sorry for the long time to post an update. It’s been 106 to 110 since I last worked on the problem. Anyway, I did get it resolved. It was either a bulb not staying tight in the socket or perhaps the 7 pin plug was not fully seated. I took the trailer and got it inspected. I did upgrade to the led lights that Scott used. They were a breeze to install, I feel a lot better about the lights. I got the led lights on Amazon, exact fit and came with the metal can. Thank you Scott!