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Battery/Generator Error(warning)

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Old Nov 9, 2019 | 03:31 PM
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Default Battery/Generator Error(warning)

Purchased my 06 S back in August (warm weather)..and as mentioned on a previous post, this was severely neglected by the previous short term owner. I am rehabbing this S back to life.
Have completed a long list of repairs...
With that said....I am in the North East and we are getting our first 20 to 30 degree weather of the season. No issues with the battery or warning messages until today. It was about 25 degrees out.
Started the S, drove for a bit and noticed the gauge for battery was not as high as its usual 15 or so. It was showing a bit under 12. At that point the Battery/Generator Error(warning) light came on.
I continued driving and the battery gauge shot back up to 15 and the warning light went off.
Two hours later, after sitting in the driveway, I decided to give the gauge another look. Started the car up and again was around 12. Battery/Generator Error(warning) came on.
I have did this multiple times throughout today and sometimes showing as 15, no warning light and sometimes as 12 and the light comes on.
Really hoping this is just the battery and not the dreaded alternator replacement.

Any comments are appreciated.
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Old Nov 9, 2019 | 03:55 PM
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Sounds like voltage regulator within the alternator.

Check this thread...
https://rennlist.com/forums/cayenne-...cayenne-s.html
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Old Nov 10, 2019 | 10:34 AM
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Once you're driving it and you get it to jump up to the normal voltage, will it fall back down to below 12 on its own during that same trip or not until the car is shut off again? If only after its shut down, many Porsches have an exciter wire that goes to the alternator and it won't have the alternator start charging until it sees a voltage spike on that wire. If your driving the car, that voltage spike can occur once your RPMs jump up to 2,000-3,000 rpm, so as you start driving the voltage is low and the warning light is on, then you accelerate, pass the voltage threshold on that exciter wire and the system starts charging normally.

I don't know if the Cayenne charging system works this way or not, but if so, that wire could have corrosion in it or at the end connections.
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Old Nov 10, 2019 | 11:35 AM
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Petza914, This error is so odd. Since my post yesterday, after multiple starts, the error has not occurred anymore.

In regards to when it was happening.......it wouldnt drop from 15 to 12 when driving, it would start at 12, sometimes go to 15. When it remained at 12, the error message would come on.
This error, is just another random error I have received since owning the S. I have received ABS warehouse brake failure messages, license plate light error messages, to name a few. These errors come on once or twice and never to be see again...
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Old Nov 10, 2019 | 12:18 PM
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If you 100% for sure know it's not your battery, then it's likely water intrusion under the carpet on the front of the car that has corroded the factory splices in those wiring bundles. You have to lift up the carpet and the very thick foam pad under the carpet and then see if there's any wetness present. Culprits are the sunroof drains, clogged front cowl drains, or the A/C condenser drain.

There's a YouTube video by P-Tech that shows him doing the removal drying and repair of this issue on a 955 model Cayenne. He works at Loeber Porsche in Chicago.
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Old Nov 10, 2019 | 02:07 PM
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Originally Posted by Petza914
If you 100% for sure know it's not your battery, then it's likely water intrusion under the carpet on the front of the car that has corroded the factory splices in those wiring bundles. You have to lift up the carpet and the very thick foam pad under the carpet and then see if there's any wetness present. Culprits are the sunroof drains, clogged front cowl drains, or the A/C condenser drain.

There's a YouTube video by P-Tech that shows him doing the removal drying and repair of this issue on a 955 model Cayenne. He works at Loeber Porsche in Chicago.
Good info, thanks. Yes, I know that P-Tech video well and also his others, good stuff.

I did test the battery with a multimeter and all looked good. Voltage was between 14 and 15 and when starting, didnt go below 10....
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Old Nov 10, 2019 | 02:55 PM
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When my alternator failed it had a similar behavior. It intermittently stopped working and started working a number of times with no pattern.
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Old Nov 10, 2019 | 07:24 PM
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Originally Posted by jgtime
Good info, thanks. Yes, I know that P-Tech video well and also his others, good stuff.

I did test the battery with a multimeter and all looked good. Voltage was between 14 and 15 and when starting, didnt go below 10....
Testing with a multi meter is not adequate, the battery should be load tested. There could be an intermittent cell. This happened to my Cayenne, eventually the battery was kaput.
Comparing with a Fluke DVM the dash voltmeter was spot on accurate.
A 12V reading indicates the battery or a connection is suspect.
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Old Nov 10, 2019 | 08:45 PM
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Originally Posted by jgtime
Good info, thanks. Yes, I know that P-Tech video well and also his others, good stuff.
You might also check the DIY section - there are about 3 threads (at least) on the subject.
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