I have an original stock 6v system with new 6v halogen headlamps. They work perfectly and are not dim or yellow. They shine as brightly and as far as modern headlights.
I think you probably have electrical problems that a relay won't fix.
What gauge wire was used in the new wiring harness?
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)
