Challenger 73 Back lights

[Husk Challenger]

Hello Guys,

I am looking to fix some gremlins in back lights.
To start, i am checking my current wires in the trunk and i campare it to the 70 one posted by @Cuda Cody in the pinned topic.

Problem i have:
No back up light when i put the rear gear.
Back up lights works when i put rear lights on.

Here are some pics of my current set up. I don't have unwrapped the wires for the moment. As you can see the back up purple wire (should be white for 73 ) has no bulb and hang in the trunk.

Blue (or fadded green)/black for left side
Brown/black for right side
No trunk ligt connected to the pigtail

I have also done a video
Here the sequence:
-Rear lights
-left turn signal
-Right turn signal
-Brake lights
-Rear + brake lights
-Rear + brake + turn signals (bug)
-R & L turn signals
-Reverse light (Nothing)
-REverse + brake light

Does anybody have a picture of a fresh and clean install?
I don't understand where my purple wire go?
Why the four lights works when i put rear lights?

EDIT:
On second thought, my rear harness looks like a 70 one, 4 lights and 1 back light 

[Chryco Psycho]

the dash light pigtail goes out through the firewall & ties into the reverse light harness from the trans so if you have reverse taillights the dash light is not connected in the right place , as you already know the 70 harness wil be a problem , you can twin the purple wire for reverse lights & not use the 2 inner light sockets

[MoparDave]

need to ground the tail lamp housing and tail panel with a clean ground to start. NOTHING will work when you have no ground. secondly. as CP mentioned check the kick panel connection. Often over looked and never checked. if you have no power on both sides of the connector. then you have a wiring issue under the dash or from the switch and or harness.

[Husk Challenger]

Thanks for the answers.

Just had the time to take pics of the current set up and compare to Wiring diagrams of 70 and 73

Kick panel connection (seems ok with 2 whites wires inside and two blacks outside)
But at the switch on the gear box i have a cut wire, where it is supposed to go? Is this the one you are talking about @Chryco Psycho when you say: "& ties into the reverse light harness"

[Husk Challenger]

Just found this on the wires from firewall to gearbox switch
..

[Chryco Psycho]

Looks like you have modified auto harness , auto used 3 wires , 4 spd used 2 , the dash light connects into the lead taking power from the switch into the trans back to the taillights so when the rear lights turn on the dash light will also .

[Husk Challenger]

Ok, i will check and test the harness!

Thank you!

[Chryco Psycho]

the area you marked Fuse with a question , is just a clip to hold the wire onto the tabs on the firewall
the harness goes across the firewall & drops down the passenger side & cross back over the top of the trans when routed properly

[Husk Challenger]

Understood.

I think mine has a custum route! 

[Husk Challenger]

Well, the reverse light works! Cool!
Just need to find the correct bulb because this one is a 24v and a new socket for the second one.

The light still doesn t work, the bulb looks good. So i think i will investigate under the dash next winter.

Thanks for help. 

[Chryco Psycho]

Glad to help , winter huh !!