How JustAnswer Works:

  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.

Ask Roman Your Own Question

Roman
Roman, Technician
Category: Audi
Satisfied Customers: 556
Experience:  over 20 years vw audi and porsche technical repair
35071616
Type Your Audi Question Here...
Roman is online now
A new question is answered every 9 seconds

Audi A6: Audi A6 2001 2.4 Quattro, after standing still for

Resolved Question:

Audi A6 2001 2.4 Quattro, after standing still for a while, it seems I have problems charging it. The battery runs low when I run the car, and when the voltage gets lower (like at 11.5V), the battery symbol starts to flash. Do I need a new alternator?


 


I should add: The car worked perfectly when I put it in the garage in April, no problems. It has not been on the road since. I just started it a couple of times to keep the battery alive, but eventually the battery ran flat anyway (maybe because it was not actually charging when the car was idling).

Submitted: 1 year ago.
Category: Audi
Expert:  Roman replied 1 year ago.
Hello ,
Here to answer automotive questions and make you feel comfortable and become familiar with your product.

1st thing to do is charge the battery, which you did.

Then if you can load test the battery you would need to check.

And finally test the alternator.

It does sound like the alternator is failing, however you will also need to check the wire connections and the cables to and from the alt. to the batt. to ensure the problem does not stem from there.

Finally after all of that you will determine if the alternator is failed.

let me know what you find and if you have any questions?
Expert:  Roman replied 1 year ago.
how is it going? have you made any progress?
Customer: replied 1 year ago.

Hi Roman,


 


Thanks for your answer.


 


I have not been home much, so I have not had a chance to perform the tests. I have managed to get a voltmeter borrowed, so I can use that.


 


If I make it home before dark tomorrow, I will perform some tests.

Expert:  Roman replied 1 year ago.
ok just let me know how you make out
Customer: replied 1 year ago.

Hi Roman,


Finally I had time and opportunity to perform some tests on the car. I will try to describe in as much detail as possible, what I do, since I think that will give you the most information to give me feedback.


 


This is the multimeter, I borrowed:



 


 


I attached the charger about 4 hours ago, and the battery was not flat, as I was able to open unlock the car doors with the remote when I got there. I did not measure the battery at that time.


Four hours later, I went to the car, started it up and measured with the voltmeter. It said 12.3v.


Then I put the red clamps around the thick black cable going to the negative pole (I am unsure if that is the correct term in English - but the minus thingy on the battery) and set the multimeter for amps. I recorded the screen of the multimeter, went into the car and used the throttle for a few seconds. The video can be seen here:


http://www.youtube.com/watch?v=6Kg5TxNILe8&feature=youtu.be


There is no sound, but it clearly increases in amps when I use the throttle and drop back down when I take my foot off.


Am I correct in understanding, that this actually means the alternator generates power and feeds it all the way to the battery? Or am I missing something?


I then proceeded to measure the voltage again and it said 12.1V. I then set the lights to parking, closed the doors and left the car idling.


30 minutes later, I went back to the car and measured the volts again. It was down to 11.0V.


I then kept the voltmeter on, put the camera on it and revved the engine. The volts increased a bit and then fell again when I took my foot off. Video: http://youtu.be/RoqR1uztuWU


Then I set it to amp-mode again, hooked it up to the negative side of the battery and did another video. http://youtu.be/0ZCmoYXdfRI Clear movement depending on throttle, not sure what to make of the numbers.


I then did a final reading of the battery, it was down to 10.4V. I turned off the car, removed the charger and came in to write this.


So to summarize the volt readings:


18.00: 12.3V
18.05: 12.1V
18.30: 11.0V
18.40: 10.4V


I am pretty confused. This is not my domain at all, but doing software development, I know how to think in logical troubleshooting and here is what it seems to me:


When the car is idling, the alternator produces less power than the car consumes (ie. the voltage drops). If the car is running at higher RPMs, it does seem to charge the battery (the amps change and the voltage increases, at least temporarily).


 


What do you make of all this?

Expert:  Roman replied 1 year ago.
It sounds as the alternator is failed internally and may only be charging at higher RPM which is not good.

You did very good!! Thanks for the detailed info.
You can double check, Make sure the leads are connected red to red and black to black.

With them connected check all the cables for corrosion and clean if present. Then bend, tug on the cables, if you see the voltage change there is a problem in the wiring if it does not change replace the alternator.
Charge the battery over night on a low rate of charge.

Customer: replied 1 year ago.

I want to do a control-measurement tomorrow of the amps, as the two I did today were so different.


 


What would be acceptable value for the charging? What should I expect to see?

Expert:  Roman replied 1 year ago.
Hi, alternator output is tested under load with a carbon pile to get a true reading. this usually a tool that the shop provides.

The tool that you have may be able to let you see some change but will not be a true reading for testing purposes.

What you can do is put your amp meter around the POS+ battery cable, start the engine and note the output then turn on the lights, ac, defrost etc. and watch the readout have someone raise the idle and watch read out again.

There should be a sticker or a stamp rating the alternator output on the side. Usually 90amp alternator is used in this car.Out put should be around 85 amps lower than that is not good. Make sure the battery is charged over night.

did your meter come with a card that explained how to do this test? That one looks like it may have that is why I ask.

Lets see what you find??
Customer: replied 1 year ago.

I did another test. First I charged the car for about 3 hours. I then hooked up the multimeter like this:


 



 


...around the positive wire.


 


I then revved the engine and recorded it. It looks like this:


 


http://www.youtube.com/watch?v=iy8hUuorY1I


 


So from 25 to 35 amps and back down.


 


Then I tried turning everything on that uses power, recorded that:


 


From 20-25 up to 45 and back down.


 


http://www.youtube.com/watch?v=0cW_WJUUfIw


 


There was nothing with the multimeter, I just borrowed it from a friend.


 


So the readings are nowhere near the 85-90 amps you mention.


 


To satisfy my curiosity and understanding here... What does this mean?


 


When the amps go up, that means there is some electricity coming from the alternator to the battery, correct?


 


If that is the case, would it be correct to say, that the alternator is not dead as such, but simply no longer delivering the power it is supposed to?


 


So if that is true, it could also be too much resistance in the cable from the alternator? That would give these symptoms, would it not?


 


I think my next step has to be to call a garage tomorrow and have them come pick it up and they can troubleshoot with proper equipment (and skill better than mine) - and change the alternator or cable, if required.

Expert:  replied 1 year ago.

Very good but let me clear some things up.

 

You are measuring the amount of current that is being output from the alternator back into the battery not out of the battery.

 

The max output from the alternator is 90 amps, when you turn on the accessory's the amperage will rise but never to 90 amps. The amperage output on your car is good. It is not putting out enough voltage from the voltage regulator inside the unit. The alternator has an output of between 13.5 and 14.8 volts. If you want to check the cable you will do what is called a voltage drop on that particular wire.

 

I have a write up on my site about voltage drop testing here. It will answer all of you questions.

 

I'm sure you will need a new alternator, you can test to satisfy your curiosity but just remember the longer that you run the engine the more you will be draining the battery.

Roman, Technician
Category: Audi
Satisfied Customers: 556
Experience: over 20 years vw audi and porsche technical repair
Roman and 3 other Audi Specialists are ready to help you
Customer: replied 1 year ago.

Ok, thanks. I will contact a local mechanic tomorrow to get it fixed. Thanks for your help. :)

JustAnswer in the News:

 
 
 
Ask-a-doc Web sites: If you've got a quick question, you can try to get an answer from sites that say they have various specialists on hand to give quick answers... Justanswer.com.
JustAnswer.com...has seen a spike since October in legal questions from readers about layoffs, unemployment and severance.
Web sites like justanswer.com/legal
...leave nothing to chance.
Traffic on JustAnswer rose 14 percent...and had nearly 400,000 page views in 30 days...inquiries related to stress, high blood pressure, drinking and heart pain jumped 33 percent.
Tory Johnson, GMA Workplace Contributor, discusses work-from-home jobs, such as JustAnswer in which verified Experts answer people’s questions.
I will tell you that...the things you have to go through to be an Expert are quite rigorous.
 
 
 

What Customers are Saying:

 
 
 
  • I would (and have) recommend your site to others I was quite satisfied with the quality of the information received, the professional with whom I interacted, and the quick response time. Thanks, and be sure that I'll be back whenever I need a question answered in a hurry. Stephanie P Elm City, NC
< Last | Next >
  • I would (and have) recommend your site to others I was quite satisfied with the quality of the information received, the professional with whom I interacted, and the quick response time. Thanks, and be sure that I'll be back whenever I need a question answered in a hurry. Stephanie P Elm City, NC
  • used your service this weekend with "Trecers" help. thank you ,thank you, thank you. replaced an A/C fan motor. Local Auto Zone had part. $15.00 "tracer" fee and $40.00 for parts, I saved several hundreds of dollers at a shop. i will recommend you and use you in the future. David L. Richmond, TX
  • 9 dollars, 2 hours of my time, and I drove away. Your diagnosis was right on the mark. Thank you so much. Phil Marysville, CA
  • Lurch. Thank you very much. I had real doubts about this website but your promptness of response, quick followup and to the point answer with picture was incredible. Charles Walnut Creek, CA
  • As a single woman, I really appreciate an excellent and affordable opinion.
    Thank you Geordie, I will not hesitate to contact justanswer in the future!
    Sue Charleston, WV
  • Another great insight to what may be the problem. I will have my mechanic take a look at it tomorrow. Thanks again, Frank...you do indeed know your stuff. Jim Castleberry, FL
  • Wonderful service, prompt, efficient, and accurate. Couldn't have asked for more. I cannot thank you enough for your help. Mary C. Freshfield, Liverpool, UK
 
 
 

Meet The Experts:

 
 
 
  • AudiDoc

    Independent Audi Shop Owner

    Satisfied Customers:

    1681
    I've been working on Audis since I was 18 and own an independent Audi repair and performance shop
< Last | Next >
  • http://ww2.justanswer.com/uploads/audidoc/2008-12-23_175252_headshot.jpg AudiDoc's Avatar

    AudiDoc

    Independent Audi Shop Owner

    Satisfied Customers:

    1681
    I've been working on Audis since I was 18 and own an independent Audi repair and performance shop
  • http://ww2.justanswer.com/uploads/35/350matt/2012-6-7_182356_matsavatr.64x64.jpg Matt's Avatar

    Matt

    Engineer

    Satisfied Customers:

    461
    Mechanical Engineer with 20 years experience in the auto industry, 8 yrs in formula 1 engine testing
  • http://ww2.justanswer.com/uploads/MI/mikeamechanic/2013-4-2_175558_photo.64x64.JPG Mike Kelly's Avatar

    Mike Kelly

    Audi Mechanic

    Satisfied Customers:

    259
    17 years experience as a auto mechanic, foreign and domestic.5 years running my own repair business.
  • http://ww2.justanswer.com/uploads/FourRingsTech/2010-01-26_135603_GetAttachment.jpg Michael Miller's Avatar

    Michael Miller

    ASE Certified Technician

    Satisfied Customers:

    241
    ASE Master Technician. Audi certified, including R8 and TDI (clean diesel).
  • http://ww2.justanswer.com/uploads/NA/nabilc/2011-1-24_205715_jap500.64x64.jpg Billy's Avatar

    Billy

    Trainer/Master tech.

    Satisfied Customers:

    229
    Trainer 8+ years, Master tech. 10+ years, SAE member
  • http://ww2.justanswer.com/uploads/tsmodie/2009-6-10_144056_tim.jpg Tim Mohr's Avatar

    Tim Mohr

    ASE MASTER TECH

    Satisfied Customers:

    204
    30 YRS EXPERIENCE, FOREIGN AND DOMESTIC, GAS AND DEISEL
  • http://ww2.justanswer.com/uploads/CA/caprio23/2011-12-13_155550_20111213105344.64x64.jpg Anthony's Avatar

    Anthony

    ASE Certified Technician

    Satisfied Customers:

    174
    ASE Master Automobile Technician with over 20 years exp. in this field.
 
 
 
Chat Now With An Audi Mechanic
Roman
Roman
Master Technician
426 Satisfied Customers
over 20 years vw audi and porsche technical repair