Ammeter NEVER shows discharge

Perhaps a prior owner did the "MAD Bypass" under the hood. Disconnect the "BAT" wire (usually thick red) from your ammeter and measure the resistance between BAT+ terminal and ALT+ (big stud). If <100 ohm, there must be a parallel path to the battery around the ammeter. If so, you might not see a discharge current, but would still measure the much larger charging current after starting.