Do you have a shop manual for your truck? It will explain how to test the voltage regulator.

Basically you bypass the VR by connecting the Field (F) or (FLD) terminal to switched power like the ignition switch. If the alternator charges the battery, the VR is most likely the problem.

Only do this for a short period of time so as not to overcharge the battery.

Last edited by Otto Skorzeny; 07/20/2025 1:33 PM.
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)