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Thread: Alternator Death

  1. #1
    Beyond Help Napalm's Avatar
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    Default Alternator Death

    So it's finally my time on my car - hoped to do this when I had the engine apart last year but couldn't get one in hand in time.

    but yesterday - start car go though the routine of getting down the sun shade, and . . . Bong Bong. Alternator on the DIC and Battery light.

    smurf me 30 miles from home. Radar Detector has a Volts display that shows volts at it's plug. and it was 10.9. drove around the lot about 2 minutes just on a whim. Presto light off volts bounce back to 13.8. car is normal.

    or so I hoped. got me home no issues. AC on, radio on, etc.

    This morning - just out of the drive way. Bong Bong - alternator on DIC and battery light.


    So I order a new one - surprised. Amazon part number correct, prime shipping 2 day. 207. total shock - nearest best price Rock Auto 221.

    Worse though - I can't get one in any store near me and I'm in the distribution center of america. Union Auto doesn't have them, GM parts counter has to ship one, Advance auto Reman - shipped (didn't want to use it anyway), etc etc.

    So hopefully come sunday afternoon I will be able to replace it and all should be good - I hope. It's orginal to the car so 08 build date. 09 Model car, 161K miles on the dash I've had it since 2011. I can't say much Gertrude has been a fantastic car.
    If Guns Kill people, then Spoons Cause Diabetes

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    Beyond Help Napalm's Avatar
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    So sunday morning and by magic I go outside and there's a box sitting at the top of my drive way. (I'm on a significant hill). HUH.

    so I wasn't able to get started till 5:45 or so and it took me a good 3 hours to get done. Biggest grief - getting the bracket bushings for the alternator and PS pump back down a tick so I could get them situated back into place. Second biggest tick my hands are clearly too big for this crap and I did have to take the tire off to get to the Positive line nut on the alternator.

    OH and of course my PS reservoir had to leak because I thought the top would stay on good. meh- live an cuss and learn.

    SO far so good - one drive down without the light coming on and battery volts reported stayed above 13.8. OH and I get to keep my old one so I will search out rebuilding.


    second best thing of the night - I found the socket I lost somehow when I did the DOD delete/lifter replacement job. WOOOO HOOO. Irony that some might find funny it's the 15 mm. The same one I needed for most of the bolts of this job - when I did the DOD job and it fell down I couldn't find it and finished the job with another socket I had. This one was my 3/8th - short. My most used. so there's 12 dollars saved as I've not bought a replacement.
    If Guns Kill people, then Spoons Cause Diabetes

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    VIP Member donkeyGT's Avatar
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    Glad you got it sorted.
    2009 GT PBM Sport/Premium Packs
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    VIP Member STL_G8GT's Avatar
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    I always quickly buy the replacement be a use that will assure that I find the lost one quickly.
    2009 PBM G8 GT
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    Mike Norris Motorsports Catchcan, AEM 30-4100, JHP Boost/Fuel Gauge Pod
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    Originally Posted by TonyKarter
    Anyone who has ever worked on a car has been in your position, and sitting cross-legged on a concrete floor with a dim shop light is its own kind of hell... Chalk it up as one of the rites of passage.
    RIP Charlie - GRRRR8
    RIP Chris Wells - Panzer Leader

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    Beyond Help Napalm's Avatar
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    Few questions now that I've played with it vs what I see in the schematic.

    When the alternator warning on the DIC comes up - voltage drops to battery line volts - the alternator is fully disengaged from the system. Is that done only with the field effect lines (the 2 wire plug on the side of the alternator) or is it done via relay and or other shunt?

    Does anyone know?

    Also using Torque app I have 2 voltage markers to read in the app - you get the same markers with other scan tools I think even HP tuners will do this. Volts (CM) and Volts (AD). as far as I know the AD is the adapter and is the voltage seen by the ODB port plug. But Volts CM I think is the commanded volts from the BCM, I know CM is command module according the the naming. But does anyone know if it is commanded from the alternator or read out from the alternator by the BCM?

    Eitherway Volts AD it a tick from being fully equal to Volts read via meter at the battery post and at the + post under the hood. The variance is well within the error range of my meter or the car I figure.
    If Guns Kill people, then Spoons Cause Diabetes

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    Beyond Help Napalm's Avatar
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    So far as I see it what I find is this.

    In the Torque APP (and in others I forget the PID code). Volts CM seems to come from the ECU/BCM somehow and I think for now it must be the volts commanded from the alternator. Reasoning - it is 0 when the engine is off. I've not yet tried to read it while starting the car and I'm not 100% sure it will anyway.

    Volts Ad - is the adapter input at the port and it tracks with battery line voltage within very small error. such as when the engine is first shut off after a second or 2 is drops to 12.7ish and then gradually falls from there. I didn't wait long but in a minute it dropped to 12.5

    With the engine running it seems that Volts CM started this morning at around 14.0-1. Note it has about 2 more decimals of fidelity than Volts AD. Volts AD follows Volts CM with a bit of lag, which could be reading timing or it could also be that the volts are propped up a moment by the battery. Eitherway Volts AD started off at 14.4 when volts CM was at 14.02ish this morning right after start.

    Only reason I'm asking and looking into this is curiosity and because I can. I'm only slightly concerned the alternator wasn't the actual problem - but it was original to the car and 10 years old with 162K miles on it. So I can't complain it didn't do it's job.
    If Guns Kill people, then Spoons Cause Diabetes

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