So one end was cut? "Somewhere" in the harness and it doesn't matter where, really, it connects into the "other yellow wires" which are in the come light circuit. There is AT LEAST three.....
One goes to each door (two)
and the third goes to the dome light switch on the headlight switch "twist the knob."
The wiring diagram someone posted may not be correct as it's not for a 68 and you may or may not have the delay relay. You can download FACTORY service manuals free at Mymopar, as well as NON factory wiring diagrams like the one posted above These diagrams are sometimes easier to follow but are not always "wire by wire" correct.
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68 Plymouth service, the Valiant info is same as Dart
http://www.mymopar.com/downloads/servicemanuals/1968_Plymouth_Service_Manual.zip
Page 333 gives you the body wiring diagram and shows the LEFT door switch at lower left
Page 340 shows the time delay relay if your car is equipped, and the MAP light switch figures in as well "if equipped"
And page 336 / 337 shows the wiring if NOT equipped with either map or time delay. This is a bit hard to trace. Find the HEADLIGHT switch on page 337, and find wire M2A-18Y coming of top, running to right and then down, it runs off the lower mid side of the page. GO TO PAGE 336 and find that wire coming INTO that page and mid right side of page.
If you follow it (M2A-18Y) clear across to the bottom left of the page, it's labeled right there as the RIGHT DOOR switch connection
RIGHT hand door switch is at top right
