See how many ring terminals are on each side of the ammeter.
On the battery side, A1D is the standard wiring connection from the bulkhead to the R terminal on the ammeter. It should have been removed (or cut and taped) when the optional wiring was installed. On the other ammeter terminal, the standard connection could have been left in place. In fact without it, I don't know how the power gets to the key switch.
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