You keep talking about "the lights"
The headlights work?
The marker / tail lights do not? Would you confirm that?
Do the dash lights work?
Jumpering from the BLACK wire is INCORRECT.
There are TWO power sources TO the light switch
I don't have a shop manual for a 75, only a 74. But there are somewhat useable diagrams here:
http://www.mymopar.com/index.php?pid=31
http://www.mymopar.com/downloads/1975/75ValiantA.jpg
http://www.mymopar.com/downloads/1975/75ValiantB.jpg
Look at the bottom right of diagram "B" and find the light switch. Find the black, top left of switch, and follow it off the left of the page.
Continue it on the right side of diagram "A" NOTICE that it splices into the BIG BLACK wire which is the black ammeter wire. This IS the factory "in harness" splice and is located a few inches down the harness from the ammeter black ring connector. It supplies ONLY the headlights, NOT the tail/ park/ dash lights
TAIL/ MARKER LIGHT (and DASH) power comes from the PINK. Look again on diagram "B", and find the pink wire on the light switch, (second terminal from bottom right) and follow it way up and off the left of the page, continuing on diagram "A" (third wire from top right) It goes to the FUSE
DASH LIGHTS. These are a trick. The dash light dimmer control gets power inside the switch from this same PINK wire, BUT the OUTPUT of the dash light dimmer comes OUT of the switch on a TAN wire, goes to the FUSE PANEL and feeds TO one lonely fuse, the "inst" fuse, and then feeds off to all the dimmer controlled dash lamps on ORANGE wiring. You can see that by looking at the fuse panel, top right of diagram "A", and the single fuse at top right. notice the TAN and ORANGE wires. NEITHER of these will show power UNLESS
1 The tail lamp fuse is good, and 2 the light switch is either in "tail" or "head." This is the only fuse in the car that operates in this fashion
According to my 74 manual, which may or may not be the same as '75, the inst. lamp fuse (3A) is cavity 1, the MAIN FUSE you need to be worried about is cavity 8, at the other end. This is a 20A fuse and feeds HORN and RELAY, provides power for INST lamps, TAIL, LICENSE, SIDE MARKERS, and PARKING
If you do not have good power to that last fuse, you won't have power to the light switch for the tail/ markers/ dash and parking.
