Weak Battery + Hot Engine - Bad Alternator?
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HT4100 4.1, 4.5, 4.9 Discussion, Weak Battery + Hot Engine - Bad Alternator? in Cadillac Engine Technical Discussion; Yeah I know that sounds like I have it backwards but don't want to jump to conclusions. Symptoms: When engine ...
  1. #1
    EldoRedo's Avatar
    EldoRedo is offline Cadillac Owners Fanatic
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    Weak Battery + Hot Engine - Bad Alternator?

    Yeah I know that sounds like I have it backwards but don't want to jump to conclusions. Symptoms: When engine is hot, and I shut off the igniton, if I try to restart the car within, say 2 minutes, the starter acts as though it just isn't getting enough juice. Turns verrry slowly -- not enough to catch. But if I come back in, say, 10 minutes or more, car starts right up!

    Finally today I had to jump it in the above situation to get it to start. Additional symptom: some rattling apparently coming from the alternator.

    Question: is the alternator not charging the battery enough, so it gets weak somehow when it gets hot??

    Battery is warrantied through May 2010 but of course it could be the culprit here -- since the DIC tonight driving home showed the battery was being charged 13.4+.

    Any thoughts?

    Thanks!

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  3. #2
    NickySantoro is offline Cadillac Owners Fanatic
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    Re: Weak Battery + Hot Engine - Bad Alternator?

    Best guess would be a failing starter, assuming all the connections are clean. I'd do a starter draw test to see if the amp draw when cranking is in spec.

  4. #3
    awadecki is offline Cadillac Owners Enthusiast
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    Re: Weak Battery + Hot Engine - Bad Alternator?

    Agree with NickySantoro. I've replaced all the starters on my 4.x engine vehicles because they have a hard time cranking when they're hot. Perfectly fine when cold. Replace the starter and you'll be fine. It's probably tired.

  5. #4
    EldoRedo's Avatar
    EldoRedo is offline Cadillac Owners Fanatic
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    Thread Starter

    Re: Weak Battery + Hot Engine - Bad Alternator?

    Again, thanks very much. I just hit 180K with this car and think I have had the original starter replaced years ago (I am second owner). Interesting phenomena that (right?) the starter becomes more vulnerable to heat over time which can end its service life.

  6. #5
    awadecki is offline Cadillac Owners Enthusiast
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    Re: Weak Battery + Hot Engine - Bad Alternator?

    Yes, they get heat soaked on these 4.x engined vehicles. Once you replace it you won't have an issue.

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