Maybe there is 12V there all the time, maybe there isn't, but from what I have learned reading about the Alta, the bike checks the resistance before supplying the voltage to each external circuit, so if your resistance is not within the expected range, then you won't get 12V out of the bike.
You used to be able to buy an OEM harness on eBay that plugs into this connector. You can search this forum, I have a thread about an "SMR". There are other threads too,
@snydes had a very good thread.