Dead short?
Thanks Redfish. I forgot to mention the short happened when the switch was switched to run .
That too, might be a clue. Unfortunately nothing on the "run" circuit is fused. The only protection is the main fuse link which is no protection at all.
Depends on the year, but what is fed by the run circuit (and of course accessory TO the fuse panel)
is the ignition system, the voltage regulator, and power to the cluster.
In 70, add the blue field lead to the alternator
THIS WOULD BE THE FIRST THING TO CHECK
WHY? Because if the brushes are damaged, or the brush holders, this can create a short right at the alternator field connection(s)
Pull both field wires off. Take an ohmeter, and check to ground. It should be infinate that is, "open" or "no" continuity.
Also the later cars (some) had other stuff added to the 'run' line. Cars with electric choke (suspect), with idle solenoids (some 340s) and retard timing solenoids on the distributors all were fed off the run line, and ARE NOT FUSED
Take a good look at the underhood harness, for any sign of "being hot" under the tape. Look carefully at wiring for melted / "crinkled" insulation
