# Battery Light & Charging Issue



## silverstoneVW03gti (Aug 27, 2011)

2012 Jetta 2.5 SE

I had an issue where the battery light was coming on & the battery wouldn't hold a charge so I replaced it with a Duralast Gold. After replacing the issue still existed so I replaced the alternator with an OEM Bosch remanufactured unit. I had the alternator tested before I left the parts store to ensure it was good to go. Got everything put back together & the battery light came on after about 2-3 minutes of run time. I thought that maybe I just had to reset the computer so I didn't think anything of it, took the car on a test drive & everything seemed to function normally. A couple of days later I left the car running for about 30 mins at idle in to see if the car would die & once again everything seemed normal. Today I went to drive the car & noticed that the car seemed sluggish while driving it, got it back home & left it running at idle & it eventually died and required a jump to get it started again. Any thoughts before I set it on fire? Thanks.


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## le0n (Jun 12, 2013)

you need to inspect your ground wires. namely, your main negative battery cable.

there are numerous other grounding locations under the hood, however, check the ones connecting to the chassis that are near the alternator.

remove, clean and reinstall. it doesn't take much corrosion to cause the ground to fail.


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## silverstoneVW03gti (Aug 27, 2011)

le0n said:


> you need to inspect your ground wires. namely, your main negative battery cable.
> 
> there are numerous other grounding locations under the hood, however, check the ones connecting to the chassis that are near the alternator.
> 
> remove, clean and reinstall. it doesn't take much corrosion to cause the ground to fail.


I'll take a look but there was only one main grounding cable going to the alternator & it was in fairly pristine condition on both ends with no corrosion. Someone else was saying that I needed to replace all of the coilpacks & wires, but I've never heard of any of those causing a charging issue. Have you?


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## le0n (Jun 12, 2013)

^^ that's good. but still remove and clean for good measure.

grounds will eat your lunch if you don't properly check them. corrosion likes to get under the crimped connectors too. the outside might look nice and clean, but the inside is what matters. for this to be happening on such a new vehicle would be rare, but not impossible.

i wouldn't change the packs, that has nothing to do with the drain/no charge symptoms.

do you have an aftermarket head unit or sound system?


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## silverstoneVW03gti (Aug 27, 2011)

le0n said:


> ^^ that's good. but still remove and clean for good measure.
> 
> grounds will eat your lunch if you don't properly check them. corrosion likes to get under the crimped connectors too. the outside might look nice and clean, but the inside is what matters. for this to be happening on such a new vehicle would be rare, but not impossible.
> 
> ...


The car is a completely stock daily driver.


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## Ronny Bensys (Apr 17, 2014)

I wonder when alternators are replaced do they include voltage regulator too? Could you measure your key-on voltage and engine-on-idle voltage? You can do this with any cheap OBDII dongle and Torque app.


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## silverstoneVW03gti (Aug 27, 2011)

Ronny Bensys said:


> I wonder when alternators are replaced do they include voltage regulator too? Could you measure your key-on voltage and engine-on-idle voltage? You can do this with any cheap OBDII dongle and Torque app.


Voltage regulators are part of the alternator these days.


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## le0n (Jun 12, 2013)

silverstoneVW03gti said:


> The car is a completely stock daily driver.


ok. i thought this sounded silly at first, but do you lock your door at night when you bring your car in the garage?

read this thread: http://www.myturbodiesel.com/threads/2012-tdi-ignition-problem.12095/
the last post is interesting. may be something you'd like to try to prove this.


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## le0n (Jun 12, 2013)

one other thought is the alt belt tensioner. not enough tension equates to not enough charging.


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## silverstoneVW03gti (Aug 27, 2011)

Went by the local auto zone today to get an idea of any codes or faulty alternator/battery. No codes were displayed, however when they tested the battery before starting the battery ready fine, after starting it read bad. Which leads me to believe that the car is drawing directly from the battery & not the alternator. Electrical mysteries of the world.


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## le0n (Jun 12, 2013)

Test or replace the alternator fuse.

Check out the last section of this thread.

http://www.myturbodiesel.com/wiki/battery-removal-and-battery-shelf-removal-on-mk5-vw-and-audi/


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## silverstoneVW03gti (Aug 27, 2011)

le0n said:


> Test or replace the alternator fuse.
> 
> Check out the last section of this thread.
> 
> http://www.myturbodiesel.com/wiki/battery-removal-and-battery-shelf-removal-on-mk5-vw-and-audi/


 I read all of that but I'm still not sure which one is the actual alternator fuse.


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## silverstoneVW03gti (Aug 27, 2011)

So I just ran a couple of basic tests on the car:

1. I pulled every fuse from the under hood fuse-box one by one and inspected them for damage/failure but nothing needed replacing.

2. I checked all of the grounding points for corrosion or looseness and everything was fine.

3. I took the belt off, used a screwdriver to stop the alternator blades from moving while I spun the alternator pulley by hand. The alternator pulley would spin with resistance in the direction towards the front of the vehicle but not towards the rear at all. 

4. With the car running I removed the positive cable from the battery to see if the car would keep running, as it should & it immediately died.

So now I'm back to wondering if the alternator is indeed bad even though I had it tested on the machine before leaving the parts store.


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## mjb8482 (Mar 4, 2008)

I think you are in the right track with the alternator. I had similar symptoms on my car a few years back and a new alternator did the trick. Not a fun job, though. 


Sent from my iPhone using Tapatalk


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## le0n (Jun 12, 2013)

silverstoneVW03gti said:


> Any thoughts before I set it on fire?


no more thoughts. just set it on fire now 

throw a capable multimeter on the alternator terminal to see if it is outputing at least 14v.

i haven't got that close and personal with the 2.5 so you may have to run a lead to where you can use the multimeter at a comfortable location.

anyway, if the alternator is giving juice directly to your meter, then you'll know there is a bad connection.

edit:
my bad, man. i missed this post.


silverstoneVW03gti said:


> I read all of that but I'm still not sure which one is the actual alternator fuse.


then you may have the fuse block that looks like this:








on some, it is one long block that houses the fuses. if one fuse goes out, you have to replace that fuse array.

on other (earlier models), the block houses the individual fuses that you can individually swap:









on either setup, the alternator lead & fuse is the one on the far left (200 amp).

definitely check that location first because i doubt your new alternator is bad. with a multimeter, just check for continuity from the base plate (where the labels: B, C, E, H, are) to the alternator terminal.

if there were attempts to jump start the vehicle, it could have blown this main fuse.


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## Ronny Bensys (Apr 17, 2014)

Additional info here.

2012 MY (not sure about engine).

Fuse 15 on fuse panel B -SB15- 30A Voltage stabilizer -J532-

It is a light-green fuse. The right one of three adjacent light-green fuses in the center of the box.


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## silverstoneVW03gti (Aug 27, 2011)

Still unable to track down 200 fuse. This is what my setup looks like:


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## Ronny Bensys (Apr 17, 2014)

This is lowline ECM. AFAIK, there isn't any dedicated alternator fuse in this layout.

I will check mine, compare to yours and will post my findings here.

Meanwhile, I would suggest checking fuses located under the dash. There are fuses there protecting various ECM modules.


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## le0n (Jun 12, 2013)

Ronny Bensys said:


> This is lowline ECM. AFAIK, there isn't any dedicated alternator fuse in this layout.


i'm under the impression that there has to be a fail-safe for the charging lead coming off of the alternator.


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## silverstoneVW03gti (Aug 27, 2011)

Yanked the alternator off last night & after some bench testing it looks like the voltage regulator is bad. Replaced it this AM & car started with the same battery light. I noticed that at idle when I rev the car above 2000RPM the light would go out so I took it out for a drive & didn't have any issues & the battery light eventually went our under 2000RPM at idle. I'm thinking that the battery was probably close to being drained from having the car running just off of the battery power before the alternator swap. I'll throw it on the trickle charger today & see what happens. Hopefully this is the last of this issue. Thanks for all of the helpful commentary.


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## le0n (Jun 12, 2013)

that sucks that the reman alt was giving those problems even after testing it before the install.

good luck, man. i hope it's resolved.


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## donjuan1jr (Oct 8, 2008)

silverstoneVW03gti said:


> Still unable to track down 200 fuse. This is what my setup looks like:


Your alternator fuse is after that black cable, and is that whole piece that the other cables attach to. 

If you have voltage on that other plug its good.


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## le0n (Jun 12, 2013)

^^ Thanks, Mike.


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## silverstoneVW03gti (Aug 27, 2011)

Kill it with fire. Full charge & battery light still comes on at idle. If I hold throttle above 2000 RPM it goes off.


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## Ronny Bensys (Apr 17, 2014)

What is your voltage at idle and at 2000 rpm now? It is time to place an ammeter between + terminal and cable, and read value at sleep, idle and 2000 rpm. Also please post your Duralast Gold ratings here.


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## le0n (Jun 12, 2013)

silverstoneVW03gti said:


> Kill it with fire. Full charge & battery light still comes on at idle. If I hold throttle above 2000 RPM it goes off.


have you checked the alternator belt tensioner just to rule it out?

have you thrown a multi-meter on the alternator to test voltage (~14v) at idle? compare that voltage to the voltage at the battery terminals. this will help rule out a bad connection between the alternator and battery.


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## Mr2phin (Nov 23, 2016)

I know this is old post. But I'm dealing with 2013 Jetta 2.5 SE having the same problem. Was wondering if you ever found a solution.


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## Ronny Bensys (Apr 17, 2014)

Mr2phin said:


> I know this is old post. But I'm dealing with 2013 Jetta 2.5 SE having the same problem. Was wondering if you ever found a solution.


Post here your measurements for current and voltage of the black cable at idle and 2000 rpm.


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## vwking (Dec 14, 2001)

It's Crazy not one person posted there fix? i have a 2015 passat 2.5 changed battery and alternator with oem unit and it only charges after you rev it over 1500 rpm maybe this is normal? the old one did the same!


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## Ronny Bensys (Apr 17, 2014)

We could have easily ruled out bad connection and GND between the battery and alternator if you tested voltage and current at idle and 2000 rpm.


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## Jpjr21 (Jun 4, 2017)

Ronny Bensys said:


> Mr2phin said:
> 
> 
> > I know this is old post. But I'm dealing with 2013 Jetta 2.5 SE having the same problem. Was wondering if you ever found a solution.
> ...


Hi guys,
First post here, but I've been a reader for a while.
How do you check that fuse? Mine isnt charging either and I replaced the voltage regulator on the alternator. I did a stupid thing and hooked up the battery backwards. Car worked before then and it still starts and runs, but wont charge. There is continutiy between the smaller black box, but not the larger one that has the black cable running to the alternator. Any help is appreciated. Battery was at 8 volts and dropping. Bad battery too, so that will be replaced.

Sorry to highjack your thread, im just at witts end trying to fix my mistake.


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## Ronny Bensys (Apr 17, 2014)

Jpjr21 said:


> Hi guys,
> First post here, but I've been a reader for a while.
> How do you check that fuse? Mine isnt charging either and I replaced the voltage regulator on the alternator. I did a stupid thing and hooked up the battery backwards. Car worked before then and it still starts and runs, but wont charge. There is continutiy between the smaller black box, but not the larger one that has the black cable running to the alternator. Any help is appreciated. Battery was at 8 volts and dropping. Bad battery too, so that will be replaced.
> 
> Sorry to highjack your thread, im just at witts end trying to fix my mistake.


Please check thin metal plates bolted under the red and black cable pins. They are 200A and 80A fuses.


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## Trizznees (Jun 24, 2017)

Hey. I did the same stupid thing. I put in a new battery and because the positive cable was black and the negative was red I ended up reversing the poles. I corrected it and the car started with no problem. However now the battery light is on. Figured I blew the alternator so I put in a new one. Still not charging the battery. I've checked every fuse and I can't figure out what the issue is. There was no issue before I put the new battery in and accidentally reversed the poles. It's a 2012 Jetta SE 4.5. Does anyone know what could cause this?


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## Challenger74 (Nov 23, 2018)

*Battery charging issue on a 2012 jetta 2.5l*

Whenever someone hooks up a replacement battery incorrectly the resulting spark is normally a sure sign that the fusible link in the underhood power distribution box has been blown. This can be checked with a DVOM. Connect the ground lead to the battery ground and after removing the cover on the distribution box check for battery voltage on the black wire. You can remove the link by removing the 3 wires towards the front of the car and 1 nut in the box. After you remove the link you can verify the open by checking for an open between the tab for the black wire and all other terminals. The cost of the fusible link is approx. 120.00 at the dealership. I believe the cost is 40.00 for the part and the rest is a moron charge for hooking the battery up backwards. :what::banghead: I hope this helps those out there that run into this problem.


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## Hanoihancock (Jun 11, 2013)

*Specifics for a noob*



Challenger74 said:


> Whenever someone hooks up a replacement battery incorrectly the resulting spark is normally a sure sign that the fusible link in the underhood power distribution box has been blown. This can be checked with a DVOM. Connect the ground lead to the battery ground and after removing the cover on the distribution box check for battery voltage on the black wire. You can remove the link by removing the 3 wires towards the front of the car and 1 nut in the box. After you remove the link you can verify the open by checking for an open between the tab for the black wire and all other terminals. The cost of the fusible link is approx. 120.00 at the dealership. I believe the cost is 40.00 for the part and the rest is a moron charge for hooking the battery up backwards. :what::banghead: I hope this helps those out there that run into this problem.


I think I understand what you are saying, but...I'm a noob when it comes to testing electrical stuff, so could you confirm my understanding is correct and answer a few follow up questions?

You are describing two separate tests, right? One to verify voltage is getting form the battery to the fuse box, and one to verify the fusible link is working, right? 

For the first test, should I test the alternator fuse with the car off, or on, or running? 

Should I use the 20V dc setting on my multi-meter? 

Should I connect the negative probe of the multi-meter directly to the negative terminal of the battery and the positive probe of the multi-meter directly to the black wire entering the fuse box?

What multi meter readings are good or bad for this test?

For the second test (once the fusible link is removed) what multi-meter setting should I use and what multi-meter readings are good or bad?

Thanks!


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## Ronny Bensys (Apr 17, 2014)

In both cases the car should be off. Use 20V DC setting. In the first test, the multimeter should read your battery voltage. If your bat. voltage is 12.5V the distribution box terminal should read 12.5V too.


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## Ronny Bensys (Apr 17, 2014)

There is a simple 5 min. test for checking alternator/battery connection. I've recommended this procedure a few times but nobody even have tried this.

1. Turn off the car. Adjust the multimeter to 20V DC.
2. Check battery voltage, should be 12.5-12.7V.
3. Start the car. Check battery voltage at idle, should be 13.6-13.8V.
4. Check the distribution box voltage, black and red wires, should be 13.6-13.8V.
5. If you want to verify if the battery is charging, you should check the current because just a 13.8V voltage on the battery is not enough for the battery to charge. Cheap multimeters are rated for < 10A so use them carefully not to blow the fuse.

If you want to check if the car is drawing current when it is off, use multimeter's Current DC.
1. Stop the engine, roll up all windows, unlock the hood, close all doors.
2. Remove positive cable from battery terminal. 
3. Ajust the multimeter to Current DC.
4. Connect multimeter's positive probe to the battery + terminal.
5. Connect multimeter's ground probe to the cable.
6. Lock the car with keyfob. Wait for 1-2 min. for the car to go sleep. Check the display.

Not sure about VW's spec but < 0.1A is acceptable.


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## TDI Kovács (Sep 4, 2012)

Wow, all this discussion and no solid fix. I understand this is the 2.5L forum but this thread is the closest I have come to a remedy.

My car has been setting since August with the same problem! With it being a TDI, it's a monster to remove the alt and I haven't yet had time to do it or attempt this nightmare. I'm afraid that I may go to all the trouble of replacing the alt and still have the same problem.

So here's some info: 2014 Jetta Sportwagen. ~32,000mi. 

Upon startup, everything is fine, alt charging @ ~14.5V at the battery for the first 10 sec.
After 10 sec, multimeter shows ~12.5V at the battery with battery light ON.
If revved to >2000 rpm, battery light goes out but still showing ~12.5V.
Car is limiting the RPM to below 2700 almost like it's in some sort of limp mode.

Here's what I tried so far:

Replaced battery with no remedy.
Checked the ground against the firewall. Test 12.5V
Checked the fuse panel (200amp, 80amp, etc.) Test 12.5V
All the wires in the fuse panel look new, no silver colored wires.
Checked the alt clutched pulley and it seems fine.

Crazy thing is, after the car ran for about 5 min, whatever started working again and ~14.5V resumed for about a minute or two then quit working.

Someone PLEASE help. To replace the alt you have to take half the engine apart. I don't want to do that if it is something else.

My fuse panel looks like this and I checked the top of each stud to the battery neg post and each showed ~12.5V.








Image credit goes to le0n, thanks for posting it.


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## Ronny Bensys (Apr 17, 2014)

TDI Kovács said:


> Someone PLEASE help.


Voltage regulator? Before removing the alternator, I suggest to check the + terminal at the alternator. Wire the multimeter to the alternator and put it somewhere on the engine cover so you can watch display as you start engine.


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## TDI Kovács (Sep 4, 2012)

Ronny Bensys said:


> Voltage regulator? Before removing the alternator, I suggest to check the + terminal at the alternator. Wire the multimeter to the alternator and put it somewhere on the engine cover so you can watch display as you start engine.


Before starting reads 12.3V from the + terminal at the alt grounded to the - at the batt.

When started immediately dropped to 12.1V from the + terminal at the alt grounded to the - at the batt.

Don't know why ~14.5V wasn't seen like usual at startup for a few seconds.

Ronny Bensys, I really appreciate your ideas.


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## Ronny Bensys (Apr 17, 2014)

Considering your low mileage and what you have done so far I'm assuming you have checked wiring harness of the alternator and the belt tensioner is ok.

Is it Valeo or Bosch?

The only thing I'm not sure is the type of the VW alternators. There are two types, with and without an actuator (relay). An alternator with actuator has a wire to activate power generation when the engine is idling. If it is an actuator type then you need to find that wire going to somewhere in the engine compartment.

Now you have two choices. Voltage regulator and bad rotor (or stator). Voltage regulators are replaceable but stators and rotors are not repairable.


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## TDI Kovács (Sep 4, 2012)

It is a Bosch alternator. I've checked as much of the wiring harness that I can get to. A friend of mine asked if there is a relay somewhere in the mix, I don't know the answer to that though. I'll have to trace more of the wiring.

I have a new Bosch alternator ready to go in. It would be great if I could swap out the voltage regulator but there is no access to it. Either way, looks like I'll be installing the new alternator soon.


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## Ronny Bensys (Apr 17, 2014)

OEM voltage regulators cost $100-120 if you go online. The dealers may have them at a higher price.

You need to remove the alternator to replace the voltage regulator. If the space between the alternator and radiator housing is little, you can try removing it from the compressor side.


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