Are my starter and alternator going bad at the same time?

[jahjelle]

I have a 2009 2.4L with a bit over 100k miles on it. A couple of weeks ago it wouldn't crank. Tried to jump it with a portable jump starter; no crank. Charged the battery overnight; no crank. Brought the battery to NAPA to test it; tested good. Put the battery back in and tapped the starter; cranked and started. This seemed straightforward enough and I bought a starter (didn't replace yet), but it continued to start just fine for the next 1.5 weeks. During that time I brought it by AutoZone and O'Reilly (for completeness, I guess?) and both ended up telling me the alternator was bad (as I recall, AutoZone said the charging current test failed, O'Reilly said the voltage regulator was bad). It was idling slow (I assume because I hadn't driven far since disconnecting the batter), so one unknown to me is if that could have influenced their tests.

A few days ago it failed to start again. Once again I tried jumping and charging - which took longer than I would have expected (so that suggested to me that maybe the alternator was failing to charge sufficiently); no crank. Tapped the starter; cranked and started. The tests from the parts stores surprised me in light of this evidence for the starter, so I took out the alternator and starter and brought them to a local auto electric shop that I've not visited before, but lots of other people seem to very happy with him. He largely concurred with the assessment that the starter seemed bad (though it worked in his testing). In contradiction to the other tests, he found the alternator to be just fine (I now wish I had asked what he checks). I thought that seemed plausible enough, but since I already had the alternator and starter out, I decided to try Advance Auto Parts. As before, the starter tested good (and the associate said it has caught some intermittent problems before), but the alternator failed (I didn't quite follow this time, but it sounded like it failed early so it didn't even try to test it). Visually, connections don't appear dirty or corroded, though I intend to clean them when I re-install parts.

I think the two incidents give me pretty good evidence that the starter is going out, but I get the impression that this seems early. Similarly, it seems unusual (at least to me) for both a starter and alternator to go bad at the same time. And I'm surprised that all three parts stores are telling me the alternator is bad (for different reasons, it seems), but the auto electric place thought it seemed fine.

Can anyone make sense of this? Are both my starter and alternator really going bad at the same time? Is there something else I could check to verify them? Is there something else that could be causing them to fail?

[tpollauf]

Welcome to GenVibe. Definitely change out the starter, but I'd hold off on the alternator. Always change one part first, usually being the most obvious. My 2004 Vibe GT had it's original starter go bad and the symptoms were a slow crank, to no crank. Luckily I was always able to "push start" as it is a manual tranny. I was almost certain that the battery was the culprit BUT after load testing it, it convinced me that it was the starter. One part at a time, and start with the starter. What part of the country are you from? Update profile for us.