Quote:
Originally Posted by Randy
The stock civic alternator has wire to turn the voltage down to 12v... basically shut off until needed, especially with a AGM battery which has a higher discharge voltage than a flooded.
Unfortunately I don't know which wire, but it goes to the ECU, and is grounded to shut off the alternator. You can just ground it with a switch to force shutoff (the ECU controls it with an open-collector circuit). I did this when I had a '94 civic. You can even monitor if the ECU has shut off the alternator by looking at the voltage: it's about 7 volts normally (you might need a 5k ohm load or so to see this), but about 0 volts when shut off. The ECU-controlled shutoff is fairly rare: it has to be warm, with no lights or fan on.
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As we have been discussing, this wire you're talking about is the alternator charging control wire. When grounded it doesn't shut off the alternator entirely. It still is charging, but at a very low rate.