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HELP! Bad Battery or Alternator???
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passatpat
New User
Jul 23, 2014, 2:48 AM
Post #1 of 9
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HELP! Bad Battery or Alternator???
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Please, any advice is helpful!
First, I drive a 1997 VW Passat with 40K (original miles, original motor)
Over the weekend, my car was dead in the morning, no headlights, no inside lights, no radio/dash lights, nothing. I had a friend jump the car, immediately upon securing the cables, the lights popped on full force & radio kicked on. All interior electrical worked immediately. A few minutes later the car was able to start and off I went, about a 20 minute drive. The car worked fine for the next 4 days, starting in the morning and afternoon to and from work. Today it was dead again.
Am I looking at a battery issue or an alternator issue? I purchased the car recently and do not know how old the battery is. The alternator is the original. I never noticed any dimming/brightening with headlights or dash lights before the car wouldn't start.
Thanks in advance!!!
(This post was edited by passatpat on Jul 23, 2014, 2:50 AM)
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jul 23, 2014, 3:01 AM
Post #2 of 9
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Re: HELP! Bad Battery or Alternator???
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Just went thru this even though long retired with a battery. Find out how old it is. They can short from inside much more likely if over 5 years old from new and plastic case is marked when it was first filled if you don't know. That's how old it is not when purchased.
Now, if it shorts a little it's just a drain unseen like leaving lights on - even a glovebox light can do this but not 100% dead just overnight on a good battery. Those somewhat rare shorts inside a battery (guess on this) can go away as it did and come back.
If an alternator works too hard and will try they get hot and don't like that at all and you can end up needing both because of one or the other depending of how failed.
I just suggest for now finding out how old battery is as you need a good known one to really test more and should quickly know if alternator is working or not when battery is known good,
T
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passatpat
New User
Jul 23, 2014, 3:22 AM
Post #4 of 9
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Re: HELP! Bad Battery or Alternator???
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Thank you both for your quick responses here, any specific things I should be looking at here for an unseen power draw? I have automatic headlights, so those certainly haven't been on, the interior lights are out, there is no glove box or glove box light either. I have noticed, however, that there is still a humming noise coming from under the hood even after the car is powered off and keys removed. I figured it had something to do with the AC and had never caused a problem (I've only owned the car since May). Is it something I'm overlooking here?
Thanks again for you help thus far!
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Hammer Time
Ultimate Carjunky
/ Moderator
Jul 23, 2014, 3:29 AM
Post #5 of 9
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Re: HELP! Bad Battery or Alternator???
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There is a procedure for finding a battery draw like that.
You will need a digital ammeter and a jumper wire with clips on the ends to do this.
First rig any door switches so you can have a door open without triggering the interior lights and unplug the hood light. Remove one battery cable and attach the meter in series between the battery cable and battery post. Take the jumper wire and also attach it the same way. Leave the jumper wire on for at least 10 minutes to expire all the automatic timers. Now remove the jumper wire and read the meter. Anything over 50ma is too much draw. The way you locate this is to start removing fuses one at a time until the meter drops to normal level. This will be the circuit with something staying on. Determine what components are part of that circuit and check them individually until the problem is isolated.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jul 23, 2014, 3:31 AM
Post #6 of 9
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Re: HELP! Bad Battery or Alternator???
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Things that might be left on as you checked some. Whatever features this car has it might have reading lamps and compartment or trunk/hatch light or a just maybe some thing via remote is staying on request like unlock and stuck there?
If parasitic draw and they sure do happen they don't always make lights stay on but something else just draining too much. It drains some (minute amount) but shouldn't kill battery in normal conditions and use. BTW - when the most used lead/acid batteries really go stone dead funky thing can happen even if recharged some are damaged by that especially if enough to cause things to reset like clock and radio it's really dead/discharged,
T
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passatpat
New User
Jul 23, 2014, 3:44 AM
Post #7 of 9
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Re: HELP! Bad Battery or Alternator???
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Thanks again, I'll certainly inspect all potential obvious power draws (reading lamps, trunk, etc) and we'll see. If need be I'll look into an ammeter for voltage readings, thank you for the suggestion.
The first time I had to jump, the clock was definitely reset. I don't have a remote lock/unlock or anything like that, but I appreciate your consideration.
I found it strange that immediately upon securing the jumper cables the first time around, all the interior lights/headlights/radio fired up full force. It was my recollection from past jumps that things like the headlights would slowly start to give off light, but mine was immediately at 100%, even though all the same electrical components were at 0% prior to hooking up the cables.
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passatpat
New User
Jul 23, 2014, 4:13 AM
Post #9 of 9
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Re: HELP! Bad Battery or Alternator???
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Of course, my mistake, thanks again!
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