Alternator not charging and battery light not on

tdisuperdave

Member
Joined
Feb 10, 2010
Location
Whitby, ON
TDI
2002 Jetta TDI
Hi, My 2002 jetta TDI is not charging (verified at battery and alternator), but battery light is off, with and without car running. Battery is good and charged. Checked all wiring including under battery box and grounds and it's OK, Grounded out the wire on the 2 wire plug for the alternator and battery light does work with ignition on. So, it's either the voltage regulator of alternator itself. Do you think I should try replacing the VR first, as it's a lot easier? Thanks


REPLY
 

amit9

Veteran Member
Joined
Oct 7, 2004
Location
Toronto/Scarborough
TDI
2003 Silver Jetta TDI GLS 5MT
A common failure part is the alternator pulley in these models. I had the same issue on my 2003, changed the pulley and it was resolved. Check that part.
 

tdisuperdave

Member
Joined
Feb 10, 2010
Location
Whitby, ON
TDI
2002 Jetta TDI
Thanks, haven't taken belt off yet, but alternator is spinning as I can see it through the holes on top of alternator, if that helps.
 

tdisuperdave

Member
Joined
Feb 10, 2010
Location
Whitby, ON
TDI
2002 Jetta TDI
Car did die with a dead battery, had to charge it back up. Alternator is spinning as seen through the holes on top of alternator. Just not sure if it's alternator, clutch, or voltage regulator. Do you know which part would more likely cause the battery light NOT to be on when it's not charging at all?
 

oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis (where it's safe)
TDI
There are just too many to list....
Bosch reman 120A alternator will fix it. I would also check the main fuse leg from the alternator to the underhood fuse link box (the one above the battery) for integrity, not melted, burnt, etc.
 

tdisuperdave

Member
Joined
Feb 10, 2010
Location
Whitby, ON
TDI
2002 Jetta TDI
Thanks, All fuses are OK including the large 150A and other ones too.
Where is the best place to buy a Bosch 120A alternator?
 

Mozambiquer

Veteran Member
Joined
Mar 21, 2015
Location
Versailles Missouri
TDI
1998 VW Jetta TDI. 1982 VW Rabbit pickup, 2001 VW Jetta TDI
Generally the Bosch alternator fails when the slip ring wears out. They're rebuildable, but I would recommend only genuine Bosch parts to rebuild.
I just rebuilt the alternator on my mk4 golf. It'll be good for another 250k miles or so.
I would not recommend getting a generic parts store one, I've seen so many of them fail prematurely.
 

tdisuperdave

Member
Joined
Feb 10, 2010
Location
Whitby, ON
TDI
2002 Jetta TDI
Update... Installed new VR with the alternator still in the car. It's a tight space, but doable. Turned key on and Battery light now works, started car and now have 14.4 V and it's charging correctly. New VR was $40, but not a Bosch. Thanks for your help!
 

Vince Waldon

Top Post Dawg
Joined
Apr 25, 2009
Location
Edmonton AB Canada
TDI
2001 ALH Jetta, 2005 BEW Wagon
How were the slip rings, when you replaced the VR/brushes?

I ask because oftentimes by the time the VR/brushes go there are deep grooves worn in the slip rings and that will be the next thing to head south. :)
 

tdisuperdave

Member
Joined
Feb 10, 2010
Location
Whitby, ON
TDI
2002 Jetta TDI
Slip rings appeared ok, still shiny, not sure about how deep the groves are compared to new, brushes were still intact just shorter after 359K kms.
 
Top