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2 occasions of alternator overcharging battery

Discussion in 'Under the Hood' started by mrau92me, February 23, 2010.

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    1. mrau92me

      mrau92me Member

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      I've had 2 occasions where my voltmeter on the dash starting indicating a high voltage condition and my info center started beeping and saying check charging system. Both times I didn't have a voltmeter to check the voltage at the battery to confirm the reading, but the problem went away after not running the engine for awhile. Both events occurred about a month apart (approx 15k miles of driving.)

      I just checked the battery's voltage with the engine running but w/ no accessories on (no a/c, no lights, no anything). I got a reading of 15.05 V. Then I got a reading of 14.99 V after cleaning the voltage reg's connection prongs. My Haynes manual says it shouldn't be over 14.5 V and if it is, change the alternator. Should I? Haynes also says the voltage regulator alone is not replaceable. Is that true? If so, why does the 'Zone's website offer it? It's priced at $70 (a little less than half for an alternator). Thx for any advice.
       
      Last edited: February 23, 2010
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    3. IZwack

      IZwack Moderator Emeritus

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      Typically, the voltage regulator is inside the alternator. So the v-reg in Autozone might work, but of course that requires disassembly of the alternator.
       
    4. eXcali

      eXcali Active Member

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      Sounds like the Voltage regulator is out on your truck. As for a replacement regulator, you can probably purchase the part, but it's actually part of your alternator in most vehicles 95+. So the theory as to why Autozone would sell you one is the same a tire salesman will sell you 6 tires if you let them.

      I wouldn't run an inline regulator with a regulator equipped alt. If you're looking to save a few bucks, pickup a rebuilt. Autozone sells these as well for about 70% of the price of new in most cases.

      Edit: Izwack beat me to it. If you're so inclined to replace the regulator inside the alt, buy an alt rebuild kit and replace the brushes etc while you're at it.
       
    5. mrau92me

      mrau92me Member

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      Do you think the 15 V reading is too much? I cleaned the regulator connection cause it had a little bit of green gunk on one of the prongs, so I thought the regulator might incorrectly be getting a low reading back from the battery so it started overcharging. Should I act now or wait to see if it spikes way too high again?
       
    6. mrau92me

      mrau92me Member

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      Alt rebuild kits don't appear to be available, only the regulator and Autozone is the only one who offers it. Makes me wonder. Also, I have 120k on the clock, so it's probably best just to buy a new alternator than to change the regulator then have to change the alt anyway when it goes bad at maybe 150k.
       
      Last edited: February 23, 2010
    7. eXcali

      eXcali Active Member

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      I'm betting that's an inline regulator.

      As far as 15volts, that's a good way to cook your battery. Chances are if your regulator is shot that you're going to be replacing your batt soon. If you take your alt up to Autozone they should be able to test it for you.
       
    8. mrau92me

      mrau92me Member

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      The battery is brand new. Had it changed about a month before all this started happening. The replaced battery was about 5 yrs old, so it was due to go out.

      BTW, Autozone's regulator doesn't look like an in-line regulator in their pic. Has 4 bolt holes in it.
       
    9. mrau92me

      mrau92me Member

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      I wonder if anyone knows if it's usually the voltage regulator that is the culprit when an alternator goes bad. If so, then it may be worth just replacing the regulator, even on a vehicle with 120k miles.
       
    10. mrau92me

      mrau92me Member

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      Update...I'm back. For this problem in early 2010, I replaced the alternator with one from Adv Auto Parts and the problem went away...until now. Now, the car has 30k more on the clock for a total of about 150k. My wife calls me yesterday and says the Mercury Mountainofcrap is beeping like crazy and showing the Check Charging System message AGAIN and it again shows overcharging on the gauge. Just the day before when I was driving it with her it beeped short beeps 3 or 4 times and showed the battery light on the last one and it didn't do it again until when she called me. She stopped at Adv Auto and they checked the system in the car and their printout said it could be the voltage reg. BTW, it's a lifetime warrantied alt. Is this a premature failure of the alternator again? Someone mentioned the PCM in another thread...any validity to that.
       
    11. Anime

      Anime EF YEAH!! Elite Explorer

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      I would say it's very likely it's the voltage regulator, not because it's a part that fails, but because it seems when anything goes wonky, the voltage regulator is damaged.

      I removed my stock alternator to replace the brushes, did so, and the alternator no longer charged the battery. Seems that in the process simply removing/replacing the voltage regulator damaged it. Either that or the sudden change from the new brushes cooked it instantly. Wound up replacing with a cheap alternator I'm not happy with.

      I would say that most aftermarket alternators, especially those with a 'lifetime warranty', aren't really up to par quality wise, and you're just getting components, like voltage regulators, that just pass spec but aren't really as good as the OE stuff. So you're more likely to get failures or flucuations in voltage, even with a voltage regulator that is working. If you've already made the plunge for a lifetime warranty unit and it's ever not working, you are usually best off using the warranty as much as you need to so you have an operating unit.

      As for the PCM, I don't think it's causing alternator issues, usually it's other electrical problems, like wire shorts, corroded wiring, etc. that do damage. It is possible to mess up the PCM with an electrical issue though, but that's still usually from operator error, such as welding with the battery connected, jump starting, or other such things that expose the electrical system to loads it's not really designed for.
       
    12. mrau92me

      mrau92me Member

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      Update. Changed out the alternator and so far all is well. Drove it about 30 miles total with no charging system alerts.

      It just seems odd to me that when my alternator has a problem, it's overcharging the battery instead of not charging it. I guess in the sense that the car still runs, it's a blessing.
       
    13. FamExploder

      FamExploder New Member

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      So I'm having a similar problem, but the battery light only comes on after about 15 mins of operatio, then the cluster cuts out, and as the revs get higher so do the volts on the dashboard voltmeter. When the lights are on they get brighter as the revs go up.
       

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