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  1. #1
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    Question How Would I Know If the Alternator Is Going Bad?

    The title explains it... I've got a 2006 Charger SRT8 with 133K on the clock... I started to have a subtle but erratic sound/feeling, almost like a misfire but not codes or pending codes... Looking for clues...

    Other info: the crank sensor was changed about 2 months ago. I noticed that the voltage in the display has spiked to 14.5 (usually not that high)...
    Last edited by richierevs; 11-20-2019 at 06:30 PM.



  2. #2
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    When mine went a couple three years ago, it was making quite a whine and my voltages were fluctuating around 12.1 - 13.5. Previously, voltages were 14 - 14.2 without headlights on.

    I removed my serpentine belt and started the car and whine was gone. Had the alternator tested and it was bad. Replaced and no more noise.
    2006 Charger Brilliant Black R/T w/R&T Package, 6.1 Arrington based 426 Hemi @ 13:1 compression 2016 Hellcat Charger rear cradle and brakes swap, DSS 4" custom driveshaft, 3.09 Scat Pack rear diff.
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  3. #3
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    As ChuckWagon points out, alternator failure root cause is overwhelmingly bearing failure, not current output.

    Current generation on these alternators is pretty well fool-proof. They are blindingly simple and robust design with no active internal electronics. Current output simply increases with rpm. The current output (duty cycle) is controlled by the PCM, based on ambient temp (as it relates to BATT charge capacity) and real-time loads.

    Edit: as to observed voltage output; again, this is a function of the PCM control circuitry. 14.5V output is normal, especially as temperatures drop to zero or below and battery charge acceptance decreases (ability to accept current dwindles because cell internal resistance increases as temperature drops)...
    Last edited by Hemissary; 11-20-2019 at 11:34 PM.
    2005 Magnum RT---Viper Venom Red----440ci Aluminum block----Short Runner Valve Intake--410mm BAER 6S Monoblock Extreme--Eibach Multi-Pro 2

    Custom--Grille Work--Hood--Headlights--Side View Mirrors--Rear Spoiler--Rear Diffuser--SRV Control System--Turbine Wheels

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  4. #4
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    Hey Simon. Way old post but follow up. I have a 2yr old battery 1 yr old alternator on mine. It sits stored on a tender. Most of the time it runs 13.9 - 14.2 driving. I noticed now it is hovering at 13.6. Think anything is going on? It is hot out but not sure how much that plays into anything.


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  5. #5
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    Quote Originally Posted by us1champ View Post
    Hey Simon. Way old post but follow up. I have a 2yr old battery 1 yr old alternator on mine. It sits stored on a tender. Most of the time it runs 13.9 - 14.2 driving. I noticed now it is hovering at 13.6. Think anything is going on? It is hot out but not sure how much that plays into anything.


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    Hi Chris, Hope all's well down your way :^)

    Sounds normal; 13.6V means the battery is more charged / fully charged. Be very warm / hot means the battery's internal resistance is actually lower. In simple terms; lower internal resistance means the battery has a higher charge-acceptance.
    2005 Magnum RT---Viper Venom Red----440ci Aluminum block----Short Runner Valve Intake--410mm BAER 6S Monoblock Extreme--Eibach Multi-Pro 2

    Custom--Grille Work--Hood--Headlights--Side View Mirrors--Rear Spoiler--Rear Diffuser--SRV Control System--Turbine Wheels


  6. #6
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    Thanks Simon

    I will keep an eye on it. Hope all is well with you also.


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  7. #7
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    Quote Originally Posted by Hemissary View Post
    As ChuckWagon points out, alternator failure root cause is overwhelmingly bearing failure, not current output.

    Current generation on these alternators is pretty well fool-proof. They are blindingly simple and robust design with no active internal electronics. Current output simply increases with rpm. The current output (duty cycle) is controlled by the PCM, based on ambient temp (as it relates to BATT charge capacity) and real-time loads.

    Edit: as to observed voltage output; again, this is a function of the PCM control circuitry. 14.5V output is normal, especially as temperatures drop to zero or below and battery charge acceptance decreases (ability to accept current dwindles because cell internal resistance increases as temperature drops)...
    Sorry to bring back up an old thread but I’m hearing a whine in the engine and removed the belt and when spinning the alternator it’s a bit harder to spin. Is it supposed to spin freely like the pulleys and stop after a second or so?
    Last edited by KStryker; 02-13-2021 at 08:38 PM. Reason: Typo

    TorRed 2007 Charger R/T, Hemi Registry #1060 (Totaled 4/10/2015)
    Brilliant Black 2010 Charger SRT8
    Appearance: CBD CF SRT8 Hood
    Performance: AirRaid CAI, Custom Tune by Johan, Corsa Xtreme, Inertia Premium Big Valve Heads, Inertia SRT MAX and Kooks LT headers.

  8. #8
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    Quote Originally Posted by KStryker View Post
    Sorry to bring back up an old thread but I’m hearing a whine in the engine and removed the belt and when spinning the alternator it’s a bit harder to spin. Is it supposed to spin freely like the pulleys and stop after a second or so?

    Absolutely nothing(!) wrong with thread revivals, the threads are where good information resides for those (like you :^) who actually search to learn / share!

    There will be (electro-mechanical) rotational resistance while in-situ. no electrical connection, it should spin fairly freely. More often than not the squeal emanates from the idler pulley.

    Taking the belt off does not really help find the squeal. Put it back together, find an empty paper towel tube or something similar, start the vehicle, put the tube to your ear and get the other end in close to each individual rotating component until you isolate which is producing the noise.

    Last edited by Hemissary; 02-13-2021 at 10:20 PM.
    2005 Magnum RT---Viper Venom Red----440ci Aluminum block----Short Runner Valve Intake--410mm BAER 6S Monoblock Extreme--Eibach Multi-Pro 2

    Custom--Grille Work--Hood--Headlights--Side View Mirrors--Rear Spoiler--Rear Diffuser--SRV Control System--Turbine Wheels

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  9. #9
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    Quote Originally Posted by Hemissary View Post

    Absolutely nothing(!) wrong with thread revivals...this is where good information resides - for all to learn / share!

    There will be rotational resistance while in-situ. no electrical connection, it should spin fairly freely. More often than not the squeal emanates from the idler pulley.

    Taking the belt off does not really help find the squeal. Put it back together, find an empty paper towel tube or something similar, start the vehicle, put the tube to your ear and get in close to each individual rotating component until you isolate which is producing the noise.

    Thanks Simon


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    TorRed 2007 Charger R/T, Hemi Registry #1060 (Totaled 4/10/2015)
    Brilliant Black 2010 Charger SRT8
    Appearance: CBD CF SRT8 Hood
    Performance: AirRaid CAI, Custom Tune by Johan, Corsa Xtreme, Inertia Premium Big Valve Heads, Inertia SRT MAX and Kooks LT headers.
    Thanks Hemissary thanked for this post

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