2001 Jetta TDI battery light on

smokemac

Well-known member
Joined
May 12, 2002
Location
Pearl City Hi
TDI
2001 jetta & 2006 jetta
When the car is cold and i start it up the battery light stays on unless i rev it passed 2200 rpm then it turns off. The battery is 8 months old so i brought the car back to Sears and they said the battery and charging system is working fine. The car starts fine and it runs great. Does any one have and idea why the light keeps coming on.
Thanks
 

Powder Hound

Top Post Dawg
Joined
Oct 25, 1999
Location
Under a Bridge, Crestview, FL, USA
TDI
'00 Golf 4dr White 5sp, '02 Jettachero 5sp, Wife's '03 NB Platinum Gray auto(!)
That light indicates a low voltage situation. If it is happening when cold, it is most likely that the alternator is having difficulties. This would indicate a replacement of the brushes (done by replacing the voltage regulator) or a rebuild is necessary. It is easily explained by considering that worn brushes, at the limit of their spring loaded travel, do not make solid contact with the slip rings until warmed up and they expand just a little.

At least that explanation makes sense to me. I don't know if that is exactly the case in your car.

A rebuild is more likely. This is because, to run the inner armature voltage, two slip rings are on the shaft. The brushes run on the slip rings. The slip rings, made of copper, will wear also because the Bosch brushes are very hard. Worn slip rings will not last, even if new brushes are provided with the voltage regulator.

Anyway, if things are checking out when tested, you might want to save up for a rebuild or alternator replacement in the near future. Don't let the battery be continuously discharged if the alternator fails or you will get to purchase a new battery also.
 

TURBO94

Well-known member
Joined
Feb 9, 2003
Location
Minnesota
TDI
Jetta, GLS, 2003, Reflex Silver
I'm not trying to steal your thread but.... this reminded me of my problem.

My battery light will flash in no pattern for a short time when I start out in the morning. It has happen 2 times in the last month.
battery is original alternator has never been touched.
I have 138,000 Miles on it I drive 60 miles one way to work so there is not alot of starting so I would think there is not alot of abuse to the Battery.
Any Ideas?
 

PDJetta

Top Post Dawg
Joined
Nov 6, 2003
Location
Northern Virginia
TDI
'04 Jetta GLS TDI Pumpe Duce Platinum Grey w/ Leather
Can new brushes be soldered into the voltage regulator? Or does the regulator have to be replaced when they wear out? If the brushes are replaceable, where can you buy them?

Tx.

--Nate
 

Powder Hound

Top Post Dawg
Joined
Oct 25, 1999
Location
Under a Bridge, Crestview, FL, USA
TDI
'00 Golf 4dr White 5sp, '02 Jettachero 5sp, Wife's '03 NB Platinum Gray auto(!)
PDJetta said:
Can new brushes be soldered into the voltage regulator? ...If the brushes are replaceable, where can you buy them?
Nate, you can get them at a well stocked hardware store. Look for brushes for small electric motors such as a drill or a buffer.

You can replace the brushes in the voltage regulator, but it will take a bit of ingenuity on your part because the part was not designed for service, only replacement. So you buy some brushes, cut them down to size, and do what it takes to get the job done.

Be sure and check the slip rings. Bosch brushes are way too hard, and by the time the brushes wear out, the slip rings are probably toast also.
 
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