Leaderboard

Yep. Installed a new battery, it was 6+ years old though it did charge back up fine. Used genius boost for starting, pulled day time running light fuse, tried to avoid brake pedal (to limit rear tail light usage). Made it home, put it on charger, drove to work today with no alt. I'll keep doing that until the ordered one arrives in the mail. 6 cylinder subaru's use a three wire alternator (4 cylinders are 2 wire and simpler) with reference voltage the ECU uses to affect alternator charging. In rare cases the alternator will put out less, like 9 volts, due to poor grounding compromising that reference signal. Measure the voltage at the battery posts and ground via the alternator body. If there's a large voltage difference there's a reference wire grounding issue. It's really rare and I assumed it was the alternator, but it was a good opportunity for me to experientially learn to test for it. I've worked on some triple digit number of Subaru's so there's a reasonable chance I'll see it some day and part of my seemingly irrelevant questions.

Check all the connections, clean and tight. Load test on the battery. Have the Alt Tested.