No headlights on '75 duster

As I said START at the dimmer switch. It's easy to get to and is in the "middle" of the circuit. IF you have power at the switch, it is either the bulkhead connector, problems in the forward harness, or a socket grounding problem out at the headlights

If you do NOT have power at the dimmer, then move up to the light switch. You should be able to work it around upside down so you can back probe the connector

You don't need the switch in the dash. You can put the plunger back in with it hanging. Be sure when you are "moving things around" up there you have the battery ground disconnected for safety

HEADLIGHT SWITCH

Looking at the switch on diagram B,

Pink, middle right, is park/ tail power coming TO the gauge from the tail fuse. This also supplies power to the instrument lamp dimmer

The unused terminal at middle left is for park lights on older cars. On newer cars, the park and tail are both hooked to the tail terminal, so the park lights are on with headlights

Top left, Black, is main headlight power coming TO the switch from the "in harness" splice. This is UNfused, as the switch has a breaker built in for the headlights. This is headlight power ONLY, and not tail, park, or dash

Top right, yellow, is the dome light switch when you twist the knob to the left. This grounds the yellow wires and turns on the dome/ courtesy lamps

Middle, light green, is headlight power going OUT of the switch to the dimmer switch

Bottom left, yellow, goes off through bulkhead to park/ marker lights. Black from same terminal, goes to rear to tail lamps


Bottom right, tan, is the dimmer controlled dash light output going TO the instrument fuse in the panel. From there it goes to all dimmer controlled dash lights

DIMMER SWITCH

The wire coming down to the switch vertically, to the right terminal, is headlight power coming TO the switch. With the headlight switch on, this terminal should be HOT

Top left, red, goes off to the high beam indicator lamp, and through the bulkhead connector to the headlight harness and to high beams

Bottom left, Violet, goes through the bulkhead connector and to the headlight harness and to low beams

SOMEWHERE out near the front of the car, radiator support, there will be an wire or two coming to a ground eyelet hooked to the body. Remove that, scrape clean and reattach, preferably with a star ground washer and new hardware.