Tail Light Woes

[DeafBringer]

Hello everyone,

I have done a search high and low on this forum, other forums, and even googled what I could. I'm not having any luck finding anything helpful (the troubleshooting guide posted here was great).

That said, I'm having issues with my rear tailights on my 2012 XL. It has the hitch witn only the 4 ping connector. I've confirmed the running lights work, 3rd brake light works, and brake switch works. The turn signals and brake lights for both the left and right tail lights do not work. Hazard on the rear also do not work. I've changed bulbs and swapped with my 2011 to confirm they work. I also checked the brake switch fuse just to make sure. I'm pretty stumped. Checked the posted wire diagrams and I'm out of ideas. Any further suggestions or tips? Thanks in advance!

 

[DeafBringer]

Still working on this. Is this the correct fuse diagram for 2012? https://fuse-box.info/ford/ford-expedition-u324-2007-2014-fuses-and-relay

Would fuse 20 and 21 (trailer tow connector) cause the brake/turn signals to not work on the rear? Really struggling to figure this out.

 

[bodabdan]

I would look for a connector that carries the brake/turn signal to the rear lighting harness, probably along the frame rail.
See if you're getting anything there and you can at least isolate it to before or after that connection. Could be a ground issue they have in common also.
Using the schematic you provided, scroll down to 2012 and it looks like #6 in the passenger compartment fusebox should power your turn signals. If third brake light responds to brake pedal, brake switch is good

 

[DeafBringer]

I assumed the turn signal fuse was fine due to the front signals working and hazards working (front only). This is a really frustrating issue for sure.

 

[bodabdan]

Good point. No matter the cause, you're either not getting good power or good ground on the back.
Could check with a test light or meter at the sockets for voltage. Can jump the ground wire to a known good ground and see if that helps.
.

 

[bodabdan]

Just checking to see if you made any progress on this?

 

[DeafBringer]

Thanks for checking, no progress so far. Been too hot. I am looking for a wiring diagram that shows me where the ground is bolted to. That way I can start there and trace back to see if I can find any breaks or issues within the harness.

I think you're onto something with the ground wire being the culprit. The running lights work great. brake and turn don't.

 

[DeafBringer]

Weather was MUCH cooler today so I took advantage. Opened up the right side interior trim of the rear quarter panel and poked around. Found 2 wires from the turn/brake/running light plug had been spliced into. I attached 2 pictures below.

Bodabdan you nailed it. They spliced into a ground wire and then regrounded it somewhere else. Then later when it was decommissioned they cut the wires, including ground. now I need to figure out which wire is ground and see if that fixes the issue. Left side looks good so far so I will focus on the right. neither pink or yellow spliced wire go to anything as they were cut.

Now to find a wiring diagram of the right side tail light.

 

[DeafBringer]

Good news: FIXED!

Turns out that 3rd wire is the power wire. It was cut into and spliced to power other accessories via the pink wire. Looped back via the yellow wire to the turn signal plug to complete circuit. Cut the Yellow/pink wire off and re-soldered and heat shrink wrapped the purple/orange wire. This fixed the turn signal, brake light, and hazard light.

Left side didn't work still so I suspected it may be the same issue. Digging into the trim on the left side revealed the same issue. Repeated the same fix for the right and problem solved.

I now have working rear brake, turn, and hazard lights! Onto other projects!

 

[AENavyVet]

Good news: FIXED!

Turns out that 3rd wire is the power wire. It was cut into and spliced to power other accessories via the pink wire. Looped back via the yellow wire to the turn signal plug to complete circuit. Cut the Yellow/pink wire off and re-soldered and heat shrink wrapped the purple/orange wire. This fixed the turn signal, brake light, and hazard light.

Left side didn't work still so I suspected it may be the same issue. Digging into the trim on the left side revealed the same issue. Repeated the same fix for the right and problem solved.

I now have working rear brake, turn, and hazard lights! Onto other projects!

Pin one is the ground, 2 goes to parking, rear license lamps, and 3 is power.