My sons dash gauges are bouncing up and down, dash idiot lights flashing off and on car occasional surges or hesitates. I've experienced this multiple times on my cars and my parents. Its always been a bad alternator. I'm assuming same for this Subaru. Tried to drive it home last night no lights on or heater fan, only emergency lights. Made it half way home - battery fully drained. Brought battery home - charged it - just picked up alternator. Heading out to do the install. Hopefully past experience is dead on.
Belt is tight, battery year old, all cables clean and tight. Hope a separate regulator is not hiding somewhere - don't know if its internal to alt.