A8 / S8 (D2 Platform) Discussion Discussion forum for the D2 Audi A8 and S8 produced from 1994-2002

What is your B+ voltage?

 
Old 08-31-2012, 08:20 AM
  #1  
AudiWorld Member
Thread Starter
 
Join Date: Aug 2012
Posts: 208
Default What is your B+ voltage?

I have now run down all of the know problems on this new 2000 A8.
Except......

Low B+ voltage problems including not charging battery and car needing jump.

Measured 13.8 at alternator running and 12.5 at battery not running.

Using the climate UP ARROW - RECIRC button codes and selecting 36.
I see at best 13.3v and worst 11.9v

I think car has bad ground somewhere causing voltage drop.

Wanted to know what volatge reading others with no voltage problems see on #36 while driving?

bonus question: what is your idle current at battery pos when car is sleeping for hours. I see 100ma+
omarcarbomb is offline  
Old 08-31-2012, 02:18 PM
  #2  
AudiWorld Super User
 
silverd2's Avatar
 
Join Date: May 2010
Location: East TN
Posts: 2,611
Default

Originally Posted by omarcarbomb View Post
I have now run down all of the know problems on this new 2000 A8.
Except......

Low B+ voltage problems including not charging battery and car needing jump.

Measured 13.8 at alternator running and 12.5 at battery not running.

Using the climate UP ARROW - RECIRC button codes and selecting 36.
I see at best 13.3v and worst 11.9v

I think car has bad ground somewhere causing voltage drop.

Wanted to know what volatge reading others with no voltage problems see on #36 while driving?

bonus question: what is your idle current at battery pos when car is sleeping for hours. I see 100ma+
I've found that the CC code #36 reading is tapped at a point away from the alternator, where it apparently already has a drain on it. On my car, that reading is always a few 10th below the actual voltage getting to my battery from the alternator...so not dependable reading for peak voltage.

The only dependable reading is at the battery with the engine running...it should be exactly what you read right at the alternator, 13.8V would be plenty to keep battery charged...anything above 13.5 would be fine. With everything "perfect", engine running and no drain ( ac off, no lights on, etc) you could get 14-14.1V, but less is still plenty to keep the battery up.

If you have less at the battery than you have at the alternator, I'd start by checking the terminal in the passengers side fender well (behind insert). If you have good voltage at the battery while running, but have trouble starting the car, I look at the battery. A battery can "look" fine (show over 12v with engine off), but fail under load.
silverd2 is offline  
Old 08-31-2012, 02:51 PM
  #3  
AudiWorld Member
Thread Starter
 
Join Date: Aug 2012
Posts: 208
Default

Thanks

I definetly have voltage drop as I move away from alternator. Already .3v down at that junction under passenger.

Is there a good list/diagram of all of the Power/GND points so I can run them all down. I hear there is one near battery as well.
omarcarbomb is offline  
Old 08-31-2012, 03:01 PM
  #4  
AudiWorld Super User
 
TSHong's Avatar
 
Join Date: May 2003
Location: Atlanta, GA
Posts: 2,057
Default

You have to look at Battery voltage and the amps output at the same time. An alternator putting out 5amps, not much will run around 14.4 volts. Now if your alternator is putting out max amps 80 or above, the voltage will drop down to 13.5 volts. They go hand in hand.
TSHong is offline  
Old 08-31-2012, 03:29 PM
  #5  
AudiWorld Super User
 
silverd2's Avatar
 
Join Date: May 2010
Location: East TN
Posts: 2,611
Default

Originally Posted by omarcarbomb View Post
Thanks

I definetly have voltage drop as I move away from alternator. Already .3v down at that junction under passenger.

Is there a good list/diagram of all of the Power/GND points so I can run them all down. I hear there is one near battery as well.
The battery ground is right next to the battery, under the tail light. But if you're detecting a drop in voltage compared to the reading on the alternator, I'd start at the alternator and work my way back...possibly clean the leads on the alternator, then on to the wheel well junction.

Did you get the .3V drop on the alternator side of the junction? If so, check the connections on the alt...if on the other side of the junction, disconnect and clean it...and so on.
silverd2 is offline  
Old 05-01-2019, 05:19 AM
  #6  
AudiWorld Newcomer
 
Join Date: May 2019
Posts: 1
Default

Two times i have faced voltage drop and both times i called electrician miami to check the issue and fix it.
LiranHershman is offline  
 
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
bballfreak
A6 / S6 (C6 Platform) Discussion
9
04-14-2019 06:59 PM
Kerry G
Audi A5 / S5 / RS5 Coupe & Cabrio (B8)
5
05-18-2018 06:12 AM
anordin2
A4 (B6 Platform) Discussion
3
02-08-2017 11:07 AM
ake11
Audi A5 / S5 / RS5 Coupe & Cabrio (B8)
5
07-04-2016 09:51 AM
jamile222
A6 / S6 (C5 Platform) Discussion
2
09-29-2015 11:22 AM


Thread Tools
Search this Thread
Quick Reply: What is your B+ voltage?


Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: