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Intermittent alternator issue

My 05 Outback has 115k miles.
I park indoors at home and work. 3 wks ago I stopped outside on my way home when it was raining. It would not start but jumped easily. On the hr drive home the lights on the dash flickered intermittently. The next day I cleaned the terminals with baking soda and water and had no problem for 3 weeks. Until yesterday, when it was raining a lot again and parked outside on the way home, it jumped easily and I drove to a big box store to replace the battery. They tested the old one that was 40 months old and it put out 3v and 0 amps. When I started at the store when they installed the new one (he also cleaned the terminals and batt compartment and applied a corrosion inhibitor) it immediately ran rough - a new condition for me. I drove around the lot and it seemed to surge somewhat and stalled once. I then immediately drove to a mechanic who tested the alternator (original). On the way it stalled twice when I was off the gas near stops. The tech said the first time the alternator showed it was not recharging, but after resetting (the gauge) and retrying it was normal. I believe he checked the belt and alt connections but I didn’t explicitly think to ask, the serprntine belt is less than 1 yr old. When I told him it had stalled he speculated that possibly the idle control was re-learning after the computer was disconnected during the batt change, among other options.

Last note, I have had other (very) intermittent electrical issues the past 3 yrs, including the dash lights all flicker whie driving, the radio volume goes up or down on its own, front left window switch won’t work, and in hot summer driving cruise cont stops during use. I do not want to ruin the new batt and dont want to lose power on the road. The stalling following the batt install doesn’t make sense to me, my dad, batt installer, or the tech.
Thanks!

Are the body and engine ground straps clean and in good condition? Some intermittent problems can result from poor ground connections.

I have never looked at straps before, and web searches have not revealed much on how many there should be or where they should connect on mine (2.5 turbo). I’ll look under the hood and perhaps the person at Advance can tell me how many and where. After searching a couple others have suggested this as a fix for unusual electrical issues like I have had also. Thanks for the suggestion.

I had no problems with the 97 Subaru I bought last year, until it “died” on her two weeks ago. Same issues with gauges/lights/stalling. Ran fine for two days after a new battery, then the same issues. Tested alternator_putting out only 10V.

When I picked up the alternator at the rebuild shop, the guy didn’t believe I hadn’t tried to fix it myself and had had no long-term problems. He charged me labor, but not for the nut that was never installed on the internal power connection to hold the ring terminal in place. The alternator was bad out of the box.

sounds like a lood=se or bad ground

“front left window switch won’t work”. I had this symptom on my '99. Replaced the alternator that was putting out all a/c current with rebuilt and replaced the switch. Perfect. No problems since then. Work was done in August 2010. Work done by local mechanic who I have learned to trust.