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Battery being drained?

Tiny
REYW31
  • MEMBER
  • 2011 VOLKSWAGEN JETTA
  • 2.0L
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 65,000 MILES
Wife came home from work for break and when she went to start the car the battery was dead.
took to auto zone it had bad cells. So I bought a new battery. As I went to install I placed battery backwards and soon realized it. So I placed it the correct way. I mention that in case that may have caused the issue if not perfect. So as I replaced the the old for a new battery everything was ok again. Car starts but the battery light was on. So I removed the alternator and took it to auto zone and they tested it a couple of times and said it was fine and had no issues. I notice the cigarette lighter fuse was burnt and replaced it. It worked. The doors would not work with key fob or the inside button, I replaced the fuse and it worked. Fuses burnt immediately and replaced them a second time and it worked again. Fuses have not burnt since but the battery drains and its brand new. Had it recharged at auto zone and reinstalled it same problem when car is running it drains the battery. When car is off no problem battery does not drain overnight. What is the problem?
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Sunday, September 6th, 2015 AT 11:11 AM

18 Replies

Tiny
CARADIODOC
  • MECHANIC
  • 33,873 POSTS
First clue: "Battery" light is on. That tells you the generator is not charging the battery while you're driving. The most you can expect is for the engine to run up to an hour; much less if the radio, heater fan, and head lights are on.

Second problem is removing the generator for testing. Generator test benches aren't strong enough to run generators under full load. Starters and generators should always be tested on the engine. By removing it, you were not able to test all the wiring associated with it.

These guides should help us fix it.

https://www.2carpros.com/articles/car-battery-dead-overnight

and

https://www.2carpros.com/articles/how-to-check-a-car-alternator

Connecting the battery backward will cause a lot of fuses to blow to protect the dozens of computers. There might still be some blown fuses that were overlooked.

What you need to do first is have the entire charging system tested with the generator on the engine. If it's not charging, a few electrical tests should point your mechanic to the circuit with the problem.
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Sunday, September 6th, 2015 AT 8:28 PM
Tiny
INVNTRR
  • MEMBER
  • 3 POSTS
Please don't assume that you caused all the problems when you reversed the Battery connection. Remember that you changed the battery because it had a problem. It may or may not still be an issue
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Monday, September 7th, 2015 AT 6:03 AM
Tiny
CMINYON05
  • MEMBER
  • 2 POSTS
  • 1999 VOLKSWAGEN JETTA
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 150,000 MILES
I've replaced the alternator, the battery, and put in alll of the correct fuses. Nothing stays on in the car, and if there is a short, I can't find it. I've been having my cousin, who is an experienced mechanic, try to fix it for over 2 months now. The car has him so confused. Any help would be great.

Christina
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Wednesday, September 30th, 2020 AT 4:43 PM (Merged)
Tiny
MMPRINCE4000
  • MECHANIC
  • 8,548 POSTS
Hook up a multimeter to battery in most sensitive DC volt mode (.01V).

Remove fuses one at a time until you find the culprit circuit.

Then disconnect each item on that circuit one at a time (radio for example) until drain disappears on multimeter.

If draining overnight, it would be a large drain, 1-2V.
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Wednesday, September 30th, 2020 AT 4:43 PM (Merged)
Tiny
CMINYON05
  • MEMBER
  • 2 POSTS
Should I do this while the car is running? We already tested all of the fuses while it is off, and we still can't find it. Any other suggestions?
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Wednesday, September 30th, 2020 AT 4:43 PM (Merged)
Tiny
MMPRINCE4000
  • MECHANIC
  • 8,548 POSTS
No, car should be off, ign. Off, otherwise the alt. Charging the battery will not allow you to find the drain.
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Wednesday, September 30th, 2020 AT 4:44 PM (Merged)
Tiny
JERWOW
  • MEMBER
  • 1 POST
  • 1998 VOLKSWAGEN JETTA
  • 4 CYL
  • 2WD
  • MANUAL
  • 135,000 MILES
Headlights recently stopped working. The windshield wipers only work when the highbeams are on. New battery wont stay charged. When I jump start car and drive around block wont start right back up. What should I do?
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Wednesday, September 30th, 2020 AT 4:44 PM (Merged)
Tiny
ALMDOG
  • MEMBER
  • 2 POSTS
I had the same problem with my 1998 Jetta. The problem turned out to be a short in the steering column related to the airbag system. My mechanic repaired it and I haven't had a problem since.
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Wednesday, September 30th, 2020 AT 4:44 PM (Merged)
Tiny
RAILLINK
  • MEMBER
  • 1 POST
  • 1995 VOLKSWAGEN JETTA
  • 6 CYL
  • 2WD
  • MANUAL
  • 264 MILES
My 95 Jetta battery drains. I use this car about every other day when I am out of town working. A local repair shop swapped some relays and said that was the problem. The fan was running too long and was draining the battery. It ran about 10 minutes each time after stopping. They did check the alternator and said it was fine. Any help?
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Wednesday, September 30th, 2020 AT 4:44 PM (Merged)
Tiny
MHPAUTOS
  • MECHANIC
  • 31,937 POSTS
You need to do a currant draw test, place an Amp meter between battery pos(+) and the cable, with doors closed and key out check the amps draw, post the findings for evaluation.
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Wednesday, September 30th, 2020 AT 4:44 PM (Merged)
Tiny
VWJOJOVW
  • MEMBER
  • 3 POSTS
  • 1984 VOLKSWAGEN JETTA
Electrical problem
1984 Volkswagen Jetta 4 cyl Front Wheel Drive Manual 180xxx miles

hello my name is Joseph and I own a 1984 Volkswagen Jetta with a 1.6 liter diesel engine. When my dad gave the car to me, I noticed that the battery light is on every time I start it. When I rev it up, the light goes away. I later discovered that the alternator is actually charging my battery. I tested using a battery charger. With the car not running, the battery was 75% charged. After 20 minutes running the car on neutral, I turned off the car, disconnected the battery from the car, used the battery charger and the battery was over 90% charged. Right now every time I'm done using the car, I disconnect the battery so that my car can run tomorrow morning. Is this bad for my car? And do I have an electrical short or is it the alternator taking power from the battery while the car is off?
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Wednesday, September 30th, 2020 AT 4:44 PM (Merged)
Tiny
DIESELLOVER
  • MEMBER
  • 13 POSTS
Hmmm, you don't give us much to go on. How old is the battery? You did clean the posts and the insides of the cable connections for 100% connection? Did you install a new radio/cd player with detachable face? If you don't disconnect the face, it will discharge your battery overnight. Do you have a multi-tester? If so, disconnect your battery cable and put the tester in between the cable end and the battery post. If your car is discharging it will show on the meter. Be sure all extra lights are off. Glove box, dome light, etc. Hope some of these suggestions are helpful to you.
Tom (I have '82 diesel Rabbit and two diesel Rabbit pickups all hopping along fine) : )
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Wednesday, September 30th, 2020 AT 4:44 PM (Merged)
Tiny
VWJOJOVW
  • MEMBER
  • 3 POSTS
The battery is fine. I found out that my car is taking away power when my car is off. It cant be any of my electronics or my A.C. Because all of them are turned off and I always take off the face from my stereo when I leave my car. What can I do to track down the thing that is draining the battery? I want to solve this myself because I heard labor on repairing a Volkswagen will cost me a ton of money. Please help.
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Wednesday, September 30th, 2020 AT 4:44 PM (Merged)
Tiny
DIESELLOVER
  • MEMBER
  • 13 POSTS
With the engine off, ignition turned off and key removed, and NOTHING electrical on to your knowledge, remove the negative battery cable from the negative battery post. Then connect a test light between the battery and the cable. If it lights up, then something is draining the battery. Go to the fuse box of the car and one by one, remove and replace the fuses until the test light goes out. When the test light goes out, you isolated the area where the drain is coming from and you'll then have to inspect whatever is on that circuit for a bare wire or somthing that is causing the drain. Good luck and I hope that helps! Merry Christmas to you and yours!
Best wishes, Tom
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Wednesday, September 30th, 2020 AT 4:44 PM (Merged)
Tiny
DIESELLOVER
  • MEMBER
  • 13 POSTS
Joseph, just had an afterthought that you don't want to overlook as a possibility. With the miles on the car, is the alternator original without any extra attention given to it? If so, it might need new brushes. These are not expensive and "easy" to replace. They make contact with the turning armature inside the alternator. With use they gradually wear down until they barely make contact with the armature. This will produce charging current at high rpm's but in start/stop town driving and low speeds, don't produce enough current to charge the battery and radio, headlights, brakelights, ac/heater blower, etc, will discharge the battery w/o the alternator recharge. Just something little, but that's what you're looking for that's causing your battery drain. Good luck and Merry Christmas! Tom
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Wednesday, September 30th, 2020 AT 4:44 PM (Merged)
Tiny
VWJOJOVW
  • MEMBER
  • 3 POSTS
Thank you Tom, and Merry Christmas to you also!
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Wednesday, September 30th, 2020 AT 4:44 PM (Merged)
Tiny
JTCUETO17
  • MEMBER
  • 1 POST
If you replace alternator does it come with new brushes or is that a separate part that has to be replaced.
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Monday, April 26th, 2021 AT 8:01 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,747 POSTS
Hi,

When you purchase a new alternator, it should be complete and ready to install. If you provide the year and model, I will get you the directions for removal and replacement.

Let me know.

Joe
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Thursday, April 29th, 2021 AT 9:18 PM

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