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Roadside Jerry
Roadside Jerry, Auto Mechanic
Category: Car
Satisfied Customers: 2948
Experience:  Auto Mehanic 39 years,30 with the NYPD Fleet Service Division
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Audi A3: my daughters battery

Customer Question

my daughter''s battery of an Audi A3 drains away and car will not turn over if car not used for as little as 2 or 3 days ,has she serious problem
Submitted: 8 years ago.
Category: Car
Expert:  Roadside Jerry replied 8 years ago.

HiCustomeryou either have a defective battery or what is called a parasitic drain,that is running your battery down. I will send you some testing information on how to check for the problem,and what must be done to find it ,if you do have a drain. You can try disconnecting the battery the next time you intend to use the car for a few days.Then if you reconnect it and find its dead,you will know the battery is the problem. If it starts you know the battery is good and can do the parasitic drain test that I am going to send. Thanks for using Just Answer,if you need more help,this question will remain open for you.Jerry.


Roadside Jerry and 5 other Car Specialists are ready to help you
Customer: replied 8 years ago.
how do I do the parasitic drain,please as there is no sign of it on my screen,please
Expert:  Roadside Jerry replied 8 years ago.

I will resend, it should have been below my answer,you have to click on it to open,let me know if it comes through,Jerry.



Expert:  Roadside Jerry replied 8 years ago.

Hi Try this one also,you can use a test lamp or a meter if you have one.

How to Find a Parasitic Battery Drain

When your car battery goes dead overnight, usually either the battery is at the end of its life span, or you left something on, such as a light. Occasionally something is drawing power that's not of your doing. This is a parasitic draw, and it can cause the same result as leaving the headlights on: a dead battery in the morning.

[edit] Steps

  1. Remove the negative side battery cable from the negative battery terminal.
  2. Attach an ammeter(this measures amperage) between the negative cable and the negative battery post. wait a few seconds to several minutes for the car to go into sleep mode. i.e. when you make the contact with the test light the cars computer systems "wake up" after a bit of time they will go to "sleep".
  3. If the ammeter is reading over 25-50 milliamps, something is using too much battery power.
  4. Go to the fuse panel(s) and remove fuses, one at a time. Pull the main fuses (higher amp ratings)last.
  5. Watch for the ammeter to drop to acceptable drain. The fuse that reduces the drain is the draw. Consult the owners' manual or service manual to find what circuits are on that fuse.
  6. Check each device (circuit) on that fuse. Stop each lamp, heater, etc. to find the drain.
  7. Repeat steps 1&2 to test your repair. The ammeter will tell you exact numbers.

EDITERS NOTE: The original author listed this repair using a 12v test light. As an ASE certified mechanic, the best place for your test light is the trash. A test light doesnt measure voltage; it shows if enough voltage is present to light the lamp.

  1. An ammeter meaures current (in amps), and that is what you are fighting against if you have a parasitic drain problem.
  2. Harbor freight sells a $3 digital multimeter (dmm) that has an amps setting. I use a Fluke, but it's whatever your trying to spend your dollars on.


[edit] Tips

  • A parasitic drain is when an electrical device is using battery power when the car is closed, and the ignition key removed. Therefore, when doing this test make sure that the dome light, under hood light, trunk light, etc. are off.


[edit] Warnings

  • Don't forget to check inside cigarette lighter and power sockets. Sometimes coins can fall in and cause shorts.
  • Some after-market alarm systems may make this test too long or loud to be worth the effort. If that's the case, seek professional help.
  • Be careful working around the battery in a car.


[edit] Things You'll Need

  • A digital multimeter or ammeter.
  • A fuse puller.
  • Any tools needed to access battery and fuse panel(s).
  • An owners' manual or maintenance manual showing electrical circuits.
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