What is draining my car battery!! **Please Help**

JettaBoy

Member
2010-09-12 7:32 am
I bought a 2002 Jetta VR6, about a two months ago and a few weeks ago it started having battery problems, now when I first tired to start my car and it wouldn't I immediately went to AutoZone and got them to check my Battery and Alternator and both tests came back perfect nothing was wrong with any of them.

So I take it back home and the next morning I try to start it up and it doesn't. So I sent it to the volkswagon dealership and they thought it might be the battery isn't the right size or alternator so they installed 2 bigger and brand new ones. And then they send it back to me, guess what ? 2 days later I still can't start,


So then I send it back again and now he says that it might be my amp in back. I've been reading some threads about this, saying that maybe my amp isn't shutting off when I turn off the car, any idea on how to fix this problem with either my Amp or the car in general ?


Things you might need to know.

1.) I bought this car used

2.) The previous owner had a aftermarket Radio installed but I don't know how much he spent on it or even how to check what it is, but the dealership says the amp is stock.

3.) New Battery

4.) New Alternator

5.) The place I bought the car won't do support for it anymore and do not have money to have people look at it right now.



Thanks a lot for any help guys,
 
first, find a new company to service your car...

This isn't brain surgery. Put an ammeter into the main battery circuit and see whats happening. If you have more than (around) 0.25A current draw when the ignition is off nd not in ACC position, you have a problem

Disconnect stuff (or switch it off) until the current craw drops to zero, or near zero.

Congratulations - you've found your problem.

Any service company who replaces the alternator an the battery on the assumption that "they aren't big enough" are idiots. Tell them so.

The only thing more foolish is accepting that this is ok - go tell them to make it right, cos they HAVEN'T fixed the problem and thats what you paid for...
 
Monitor the battery current as mentioned and see if there is excessive battery drain. If the current looks excessive, go to the car's fuse block/s (there may be more than one - check the manual), and start pulling fuses until the excessive drain goes away. That will at least localize the problem. I had a problem with the turn signal stem on my PT Cruiser that would cause the fog lights to turn on randomly and drain the battery if I didn't catch it in time. Sooner or later, I'll need to replace the turn signal stem that contains the switch for the fog lamps, but I'm a lazy git, so I pulled the fuse for the fog lamps (usually don't need 'em) and have had no problems since.
 
>the volkswagon dealership and they thought it might be the battery isn't the >right size or alternator so they installed 2 bigger and brand new ones


Whatever you do, don't go back to that shop unless its to collect money. Putting an ammeter in series with the battery and then pulling fuses one by one is a good starting point. One time I got booby trapped like this by a new used car. It turned out the brake light switch adjustment had moved so that when the moon was right it would never shut off even if I got out of the car.
 
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Mooly

Administrator
Paid Member
2007-09-15 8:14 am
Something weirds going on... a new battery, let's say 60ah capacity and you leave it overnight and it doesn't start... that's some leakage current to do that, even drawing 2 to 3 amps for 12 hours or so and it should still start.
An old battery is a different matter and even a few 100 milliamps draw can see one off to the point of not starting... but your's isn't.
Can you feel this amp warm when it's off because that sort of power drain will cause heating.
I would disconnect this amp if you are not sure how to measure the current to it and see what happens.
Have you confirmed the alternator and battery really are new.
Be very carefull measuring current directly from the battery, it's easy to zap a DVM if for example the central locking activates etc as the current draw is huge.
Any luggage lights ? dicky switch.
 
O geez I didn't even read that you have a custom audio system. Absolutely, for starters, isolate the audio system. The dealership should have at Least been able to tell you that's where the problem is, if it is, and ask you to take it to a place that deals with that stuff.

If you have no test equipment, take the power down from the audio system when you leave the car overnight. You can remove fuses from amp supply lines if you want to just troubleshoot that first, or you can come back and check for heat as Mooly suggested.
 
1-Close all of the doors on your car except the trunk, leave it open
2-Disable/disconnect the trunk light (if it has one) and make sure all dome lights are off
3-Disconnect the battery ground cable and connect an amp meter between the battery ground wire and terminal. Make sure your amp meter is set on the 10 amp setting with the +/red lead in the 10 amp high current test hole
4-Watch current draw, it should stabilize to .05 amperes or less within two or three minutes
5-If current draw stays above that, pull the fuse from your car amp in the trunk. Now go back and check the amp meter to see if it drops to a normal level.

The guy who installed the previous system could have connected the trigger lead incorrectly to a speaker wire behind the deck or a constant. The amp could also have a defective internal circuit causing it to stay on.
 
post number 2 is dead on i'm a master tech with many years under my belt listen to no one else and follow his instructions. just note most newer cars have control units that may stay on for up to 20mins. so hook up amp meter wait 30 mins then look at the curent draw. also just opening the door can wake up some control units
 
...just note most newer cars have control units that may stay on for up to 20mins. so hook up amp meter wait 30 mins then look at the curent draw. also just opening the door can wake up some control units

Absolutely! In other words, unlock the car, leave all the doors/trunk/hood open, and walk away for 1/2 hour. Then start to fiddle around-but DO NOT close any doors, switch any lights, etc, as that will wake up the car again.

I agree it sounds like the aftermarket radio may be keeping the amplifier on via miswiring. To the poster who talked about 2-3 amp shouldn't kill the battery: you're right, but if the amp is kept on it is possible the entire car is kept awake. Not sure in this Jetta's case, but encountered that with some BMW & Benz protos. Keeping one component alive prevented the bus from shutting down, in one case keeping the trans continuously drawing like 10A!

I don't know where the amp is-try VW/Jetta forums for that, I'm sure someone knows.
 
As others have said, check the radio wiring. The turn on lead for the amp is wired wrong and the amp is not shutting off. A three amp drain will kill a battery, also, it will ruin the battery to constantly drain it below 10 volts several times. Only deep cycle batteries can recover from deep discharge in the range of 60 times before it starts to suffer damage.

Just have the radio properly wired. VW do not have a switched lead from the key to the radio and most aftermarket radios need that for total shutdown. You can tap the heater circuit for that on the key but there is no acc. position so the radio will only play in the ingnition on position.

Look on the bright side, you now have a high output alternator to power a killer system. ;)
 

infinia

Member
2005-05-15 9:51 am
SoCal
So I take it back home and the next morning I try to start it up and it doesn't. So I sent it to the volkswagon dealership and they thought it might be the battery isn't the right size or alternator so they installed 2 bigger and brand new ones. And then they send it back to me, guess what ? 2 days later I still can't start,

I love this, troubleshooting by a service adviser ie sell em more sh1T.

If this were me I'd have a field day on this "stealer" service dept.

1. Take it back (with a lawyer hat on) and have them pull out what they said would fix the problem and find the original problem with a real tech. Request a different service supervisor then make sure to specify a tech with some electrical specialty does the work. Make sure they write down exactly what was said and done before on the new paperwork. LOL
2.
 
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Pretty much every vw we worked on (at Circuit City) had a switched acc12v+ for the oem radio, I'm sure many of their new vehicles are CAN bus but they weren't doing that on all of the models we did at least as of 09. I'm sure there were models with it but it depends on which model vw you have. Not every car uses that system for the radio, even most of the new Toyotas still run a normal 12v acc power on for the radio. Now after going back and reading the first post again I'm pretty sure there is no CAN bus system in your 02 vw.

<----Toyota tech