Assuming stock headlight wiring which has a 3 position terminal board on the driver's side inner fender near the front ...
Attach a long wire to battery + with the other end stripped back just 1/4 inch or so. Touch one terminal at a time and see what happens on the front of the truck. One is high beam, one is low beam and one is for the parking light.
Because your high beams work, you have proven the circuit is good from the battery, through the headlight switch and down to the common terminal on the dimmer switch.
Following your advice, I connected a hot wire from the battery to each of the three terminals. The lights came on each time. I couldn't tell if the brightness changed between either terminal
1950 Chevrolet 3100 (Ol' Roy)
1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)
