indignation = In the ignition? ? Spell check wins another one. ?
First see if you can twist the battery terminals without loosening. If so, they need to be shimmed (bad connection).
Next I'd check for bad/corroded connections or grounds on those large cables. The ends AWAY from the battery are suspect, too. If you have jumper cables, securely connect ONE from the engine to the battery ( - ) terminal for a few days as a diagnostic. If that resolves the issue you need to do more digging. If not, you can move on, because you have eliminated the Ground side of the circuits. (Frankly, it sounds like an issue on the Positive side of the circuit, though)
Post back with results.
First see if you can twist the battery terminals without loosening. If so, they need to be shimmed (bad connection).
Next I'd check for bad/corroded connections or grounds on those large cables. The ends AWAY from the battery are suspect, too. If you have jumper cables, securely connect ONE from the engine to the battery ( - ) terminal for a few days as a diagnostic. If that resolves the issue you need to do more digging. If not, you can move on, because you have eliminated the Ground side of the circuits. (Frankly, it sounds like an issue on the Positive side of the circuit, though)
Post back with results.