I'm having an issue with my entire rear light system. My brake lights, blinkers, tailgate lights, etc. are all out. They come back on intermittently, so I don't think it's a fuse. I think there's an issue with wiring somewhere. Occasionally, when I hit a bump, the lights will start working again. We're just outside of 36,000 miles, so the Ford dealership is wanting to charge $99 to just look at it. I'm pretty savvy with electronics, so I think I could fix it if someone could point me in the right direction as to where to look for an issue. Thanks in advance for your help.

 

Check for a loose ground. I'd pull one of the light assemblies off and shake the wiring while you have the lights turned on and just follow the wiring loom checking for loose ground connection somewhere.

I saw a wiring diagram on another post that shows a common ground between both sides. Not sure where its actually located but check around back there.



From another forum..... G 400 common ground is located....


"found it. left frame rail in front of fuel pump, bad ground
reattached and all works fine"

 

Another body ground point is located at the battery in the engine compartment. Others have found this to be a problem as well.

 

Definitely a poor or loose electrical ground or even a loose positive power connection somewhere... but definitely a grounding issue

 

Y'all were right! When I saw artsr2002 mention ground, I remembered having to adjust a ground wire to install my trailer hitch. Sure enough, the bolt that connects that wire was loose. I tightened it back up and added some electrical tape for good measure, and it's working again! Thank you all!