73 Dart Alternator doesn't show charge anymore.

Look at the key.
The violet wire is for the horn. H1 16V => Horn 1, 16 gage wire, Violet insulation.

There's a 1974 Master Tech filmstrip and booklet about wiring diagrams. It covers the new style of diagrams introduced in 1973 and explains all of the wire codes.
pdf version here: Browse MTSC by Model Year – 1974 – MyMopar
These later diagrams are hard to keep track of individual circuits. Use the diagram to make your own drawing of just the circuit(s) you are interested in.

Complete listing of the Master Booklets and films is here:
Master Technician Service Conference - Chrysler's Training for Mechanics
Once you know the year to look under you may want to go to back to the mymopar website to view them in pdf format.