Battery/ Generator light on DD Need your opinions

RallySport

Well-known member
Joined
Apr 5, 2017
Location
Washington Twp, MI
TDI
2002 Golf TDI ALH
2002 ALH Golf 5 speed.

I need help with diag on my daily. My battery/generator light is coming on and off. It stays on most of the time now. I just started having this issue yesterday.

i feel a rougher idle than normal. It doesnt really seem like the alternator is bad because it got me all the way to work and back (70 miles round) the car drives like it should for the exception of the generator light and my battery was pouring out steam or something... there is a VERY FOUL odor because of whats going on witg my car now. Smells like somethings melting..

Instrument cluster seems to become inop when you accelerate and will flicker back to life and then off again in a quick time frame. This happened on my whole way home.

I dont have a voltmeter right now and i havent even begun the basic tests but im posting here to hear anyone elses experiences with the generator light coming on with similsr issues.

Before i started having this problem i thought i had an ac clutch pulley on its way out. It wasnt real bad but you could hear it. Now since the generator light has come on i can DEFFINITELY hear a bad pulley.. could be the ac or the alternator. May or may not be 2 differemt issues.

When i get a hold of a voltmeter i can check the bsttery voltage and the output of the alternator. Its unlikely the battery is bad as i have replaced it last winter but its an oreillys battery.. not the bigger battery it should have.
 

Vince Waldon

Top Post Dawg
Joined
Apr 25, 2009
Location
Edmonton AB Canada
TDI
2001 ALH Jetta, 2003 ALH Wagon, 2005 BEW Wagon
The foul odor might be hydrogen gas... and a little sulfate... aka hydrogen sulfide (what gives rotten eggs their smell) which means your battery is being seriously overcharged and is boiling over. Or the smell of something cooking electrically.

Not much you can do till you get a voltmeter, but it's likely that the alternator is misbehaving and you'll see voltages at 16V or higher.

It's your DD but if you keep driving it in this state you'll likely need a new battery to go with your new alternator. :(:)

Once you get a voltmeter, the measurements to check are:

1) at the battery posts, engine off: voltage 12.5 or thereabouts

2) at the battery posts, engine started: voltage jumps to 13.5-14.5v at the most

Anything more than 14.5 or less that 13.5 and your alternator needs repair/replacement.
 

WildChild80

Veteran Member
Joined
May 30, 2016
Location
Nashville, AR
TDI
2001 Jetta TDI 2000 Jetta TDI 2000 New Beetle TDI ALL 5 speeds
Does it ever make a metallic sound like a grinding or screeching? I had my decoupler stop working after my dad let my car sit for 2 months

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PakProtector

Veteran Member
Joined
Jan 5, 2014
Location
AnnArbor, MI
TDI
Mk.4's and the Cummins
If it is overcharging, the regulator/brush assy is bad. It is a simple fix, and does not require much time either. There are detailed instructions for the repair, the best I found was right here, but I found it with Google. Step by step with pictures( with circles and arrows and a paragraph on the back of each one ).
cheers,
Douglas
 

BobnOH

not-a-mechanic
Joined
May 29, 2004
Location
central Ohio
TDI
New Beetle 2003 manual
This is potentially dangerous. Some good interweb guesses so far.
.................... and my battery was pouring out steam or something... .....................
Occasionally a battery case will rupture, the fumes are highly flammable, not to mention what the acid can do. I wouldn't drive it it until you get this sorted out.
Sounds like 2 separate issues, but if acid got slung around in the engine compartment, it will eat thru whatever it contacts.
PROCEED WITH CAUTION.
 

derek5120

Veteran Member
Joined
Sep 25, 2014
Location
Arthur Ont.
TDI
2003 jetta GLS
You should get your battery load tested also, when batteries short out inside they act like a load, the alternator responds by upping it's output. Gassing batteries are dangerous, wouldn't recommend driving it.
 

RallySport

Well-known member
Joined
Apr 5, 2017
Location
Washington Twp, MI
TDI
2002 Golf TDI ALH
Charge voltage 17v

So i had to take the battery out of the car..
its a POS Oreilly battery 650 cca..
the voltage of my battery was .2 or .5 after sitting. It was cold and dead so i took it to oreilly they "tested the battery".. said it was still good..
the battery was reading 12.5 after i hooked it back up. Started her up and the alternator was pumping 17 volts!!!! Im lucky i didnt blow the battery up driving it home from work.

Side note; one shorter side of the battery case was bulged... the side that was pouring with the acid/smoke. Im worried this battery may not be safe..

Also to document here on the forum i watched the serp tensioner going crazy shaking. It seemed as id like something was interfering the alternator pulley.BAD.. (linear with the pulley system)

Can anyone chip in with a similar experience?
I believe my problem is the alternator.
 

Vince Waldon

Top Post Dawg
Joined
Apr 25, 2009
Location
Edmonton AB Canada
TDI
2001 ALH Jetta, 2003 ALH Wagon, 2005 BEW Wagon
Anything more than 14.5 or less that 13.5 and your alternator needs repair/replacement.
Since it's an over-voltage the regulator internal to the alternator is the prime suspect.

It can be replaced independent of the alternator, but it's worth checking the slip rings on the alternator before putting money into a new regulator. If the slip rings have any serious wear it will probably be cheaper to get an entire replacement alternator.
 

Ol'Rattler

Top Post Dawg
Joined
Jul 3, 2007
Location
PNA
TDI
2006 BRM Jetta
Also to document here on the forum i watched the serp tensioner going crazy shaking. It seemed as id like something was interfering the alternator pulley.BAD.. (linear with the pulley system)
Can anyone chip in with a similar experience?
I believe my problem is the alternator.
Your over running clutched alternator pulley is seized.
 

WildChild80

Veteran Member
Joined
May 30, 2016
Location
Nashville, AR
TDI
2001 Jetta TDI 2000 Jetta TDI 2000 New Beetle TDI ALL 5 speeds
One vote for a new unit.

You'll be close to a new alternator by the time you replace the over run pulley and voltage regulator

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[486]

Top Post Dawg
Joined
Mar 1, 2014
Location
MN
TDI
02 golf ALH
I'd look for a junkyard alt, lots of them got a lifetime warranty that rolls over to the replacements and they're like $40. Oddly the 120A manual trans alt is a lot cheaper than the 90A auto, so there's even no reason to get the smaller alt.

the steam and stink is pretty normal for an overvolted battery, your alt is probably full-fielding. Use the 10mm wrench in the spare tire kit to remove the fuse in the battery fusebox that goes to the fat black wire. This will keep the alt from killing the new battery too while you're running around sourcing the new alternator.
 

WildChild80

Veteran Member
Joined
May 30, 2016
Location
Nashville, AR
TDI
2001 Jetta TDI 2000 Jetta TDI 2000 New Beetle TDI ALL 5 speeds
I'd look for a junkyard alt, lots of them got a lifetime warranty that rolls over to the replacements and they're like $40. Oddly the 120A manual trans alt is a lot cheaper than the 90A auto, so there's even no reason to get the smaller alt.

the steam and stink is pretty normal for an overvolted battery, your alt is probably full-fielding. Use the 10mm wrench in the spare tire kit to remove the fuse in the battery fusebox that goes to the fat black wire. This will keep the alt from killing the new battery too while you're running around sourcing the new alternator.
I'm glad I'm not the only one...went for the transmission (5 speed) and ended with an alternator, starter, turbo and the transmission for 120 or so...I was a happy camper

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wonneber

Top Post Dawg
Joined
Oct 12, 2011
Location
Monroe, NY, USA
TDI
2014 Jetta Sportwagon,2003 Jetta 261K Sold but not forgotten
A bad ground use to cause the old alternators to charge high.
Not sure if that's still the case.

With the car running and lights on measure the voltage from the negative post of the battery and the case of the alternator.

I would not want to see more then a few tenths of a volt.
 

joyee

New member
Joined
Oct 23, 2004
Had a similar issue with my 2003 Golf at 275k miles. Battery light came on. Checked battery voltage and it was 12.4v. With engine on, it would oscillate between 12.4 and 13.5 causing the idle to dip each time the alternator created a load. Bought a replacement regulator off Amazon for $20 and it took care of problem. Didn’t have to remove alternator to replace regulator. Noticed one of the carbon brushes was shorter than the other perhaps causing the problem. Both were quite worn compared to new.
 

RallySport

Well-known member
Joined
Apr 5, 2017
Location
Washington Twp, MI
TDI
2002 Golf TDI ALH
Okay got around to putting a new Valeo Alternator into my golf this past Saturday.

I will say that the R&R for an alternator, is a piece of swiss cheese thanks to this fantastic forum! It appears to have fixed the overcharge issue.

I still have a blown blade fuse on the battery fuse box.

My lowbeam headlights are not operating. Could this be because of a blown fuse at the battery?

The small post terminal was pretty corroded when i took the small 8mm nut and washer off of the old alternator, is this one of the main grounds for the alternator? I dont THINK that this small ground terminal would cause the alt to overcharge as much as it was.

Theres a screw on the front of my old alternator(right behind the edge of the pulley) that was backed out all the way so something could be loose in the alternator. I'm going to guess that it was the voltage regulator.

SHOULD I REBUILD MY ORIGINAL ONE AND SELL?
 

wonneber

Top Post Dawg
Joined
Oct 12, 2011
Location
Monroe, NY, USA
TDI
2014 Jetta Sportwagon,2003 Jetta 261K Sold but not forgotten
The low beam lights use fuses 20 and 21 inside the car.
One fuse for each side.
 
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