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Discussion Starter #1
I've been trying to diagnose a strange electrical issue with my T3 and decided to measure voltage from the 12 volt outlet in the vehicle with my Fluke.

What should I be reading as a normal voltage? At idle, its around 14.8 volts but when driving (higher revs), I see it hang around 15 to 15.1 volts and spike at 15.4 or higher.

I always thought it should be between 13.5 and 14 volts?

Thanks!
 

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Discussion Starter #2
I also verified that I am getting the same measurements from the jumper posts under the hood.

It appears that within 10 seconds of starting, it settles in right between 13.5 and 14 - 14.2 volts. The longer I drive it, the higher it goes and seems to peak at nearly 15.5+ volts while driving and does not come down. At this point is when I experience strange electrical issues. It originally started as relay clicking noises, but yesterday after driving for 30 minutes I saw warning messages stating AFS was disabled, auto hill hold was disabled and ESC (ASR) was disabled - only for 1 second...then returned normal.

I believe my alternator/regulator is suspect now, but would like to know what should be normal readings. Going to dealer on Monday and they'll have it for the week while I'm out of town for business. Just trying to point them in the right direction as it can be an intermittent problem.

Thanks.
 

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15.5 is, I believe, abnormally high. I checked the manuals, and none specify proper voltage for the system, but I'd expect something in the 13.5-14.5 range would be normal. Check the B+ lead on your alternator for tightness and corrosion. Ditto for your battery terminals - check to ensure they are tight and there is no visible corrosion. If all looks good, you may have a dying alternator volt regulator.
 

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The symptoms point to a voltage regulation problem. 'Normal' is for the voltage to peak while the alternator is recharging the battery form the start sequence with an ending steady state 'engine running' voltage of about 14.7 - 14.8 V. Any increase after that would have to be explained by a large increase in electrical load.
The VW Touareg electrical system is complicated and MAY have built in features to protect against voltage which is too high. Thus the tripping off of the ABS, cruise control, etc.
The regulator built into the alternator is suspect.
 

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Discussion Starter #5
FWIW, here is a video that shows the spikes. Sitting in park with slightly increased rpms off idle. Towards the end shows idle voltage...around 14.7 - 14.8.

Currently at dealership..

 

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Discussion Starter #6
Spoke to dealer and they confirmed with VW these is a normal voltage range. Per VW this can range from 14.x volts up to a max of 16 volts.

Original issue is suspected to be a loose ground in the dash.
 
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