Dome light...

Useable wiring diagrams from MyMopar:

http://www.mymopar.com/downloads/1973/73ValiantA.jpg

http://www.mymopar.com/downloads/1973/73ValiantB.jpg

came from here:

http://www.mymopar.com/index.php?pid=31

Generally, YELLOW is the ground side of the dome light, IE the door switches ground that side to activate the light. Yours may have a time delay relay

I haven't researched this completely, and do not have a 73 shop manual, it might also be a backfeed problem if you have the headlight warning buzzer.

Start by making SURE your headlight switch dash lights dimmer is NOT over into the courtesy lamp position, and nex disconnecting one door switch at a time, as well as the delay relay if you have it, and the warning buzzer if you have on.

I SURE WISH you guys who have 73/4 shop manuals would get ahold of Abodyjoe and post 'em here.