Alternator Slip Ring Wear

chirishboy

Veteran Member
Joined
Mar 25, 2009
Location
Houston, TX
TDI
2001 Jetta TDI 5spd
Typically 11.5 - 12.15 v at the battery terminals at startup but would typically return to +14v after the engine warmed up. After replacing the regulator it improved to 14v consistently even when cold but the last few days has been consistently <12.5v even when warm.
 

993er

Veteran Member
Joined
Oct 10, 2013
Location
Canada
TDI
None
Typically 11.5 - 12.15 v at the battery terminals at startup.
During cranking of the engine, a lower voltage is normal due to the load and increased current. But that just takes a second. BTW, hard to measure since the load varies unless you have a storage scope or DMM with max min hold.

You should always be getting 14.0 to 14.4V above idle and depending on the load. When cold, those numbers will be slightly higher and when hot, in the upper 13s.

Maybe your diode pack in the alternator is acting up once hot. Then your DC has some partial AC on it.
 

KLXD

Top Post Dawg
Joined
Aug 22, 2009
Location
Lompoc, CA
TDI
'98, '2 Jettas
Those rings don't look bad but how are the brushes? Mine had grooves at least 1/16" deep when I got the charge light but the brushes were worn too so there was poor contact.

I got another week out of them by pulling on the brushes to stretch and straighten their wires so they wouldn't try to pull them away from the rings.
 

TheKid760

Member
Joined
Mar 1, 2012
Location
PNW
TDI
2003 MK4 Jetta Wagon
Update:
Has been 35k miles since the rebuild. Everything still running well.
 

Mozambiquer

Vendor , w/Business number
Joined
Mar 21, 2015
Location
Versailles Missouri
TDI
2004 VW Touareg V10 TDI, 2012 Audi Q7 V6 TDI, 1998 VW Jetta TDI. 1982 VW Rabbit pickup, 2001 VW Jetta TDI, 2005 VW Passat wagon TDI X3, 2001 VW golf TDI, 1980 VW rabbit pickup,
Thats great! I rebuild these fairly often. The shop I used to work at simply replaced the rotor if the slip rings were worn, but I learned to do it myself. I get the oem bearings, slip rings and regulators making it as close to oem quality as I can.
 

DCM1

Well-known member
Joined
Jul 6, 2022
Location
BC
TDI
2001 Jetta sedan 5 speed
I skimmed the thread and didn’t see it anywhere, but if a person is looking for aftermarket sealed bearings, it’ll be the bearing number followed by “2RS”. Shielded bearings will be the number followed be “ZZ”.
 

TheKid760

Member
Joined
Mar 1, 2012
Location
PNW
TDI
2003 MK4 Jetta Wagon
I skimmed the thread and didn’t see it anywhere, but if a person is looking for aftermarket sealed bearings, it’ll be the bearing number followed by “2RS”. Shielded bearings will be the number followed be “ZZ”.

 

Mozambiquer

Vendor , w/Business number
Joined
Mar 21, 2015
Location
Versailles Missouri
TDI
2004 VW Touareg V10 TDI, 2012 Audi Q7 V6 TDI, 1998 VW Jetta TDI. 1982 VW Rabbit pickup, 2001 VW Jetta TDI, 2005 VW Passat wagon TDI X3, 2001 VW golf TDI, 1980 VW rabbit pickup,

markdave

Well-known member
Joined
Jan 13, 2023
Location
amesterdam
TDI
tdi 1.6
The slip rings are badly worn, but new slip rings are available for a modest price and are easy to replace, so why scrap the whole alternator?
 
Last edited:

annamartino

Member
Joined
Jan 18, 2023
Location
amesterdam
TDI
1.6
The slip rings are badly worn, but new slip rings are available for a modest price and are easy to replace, so why scrap the whole alternator?



 
Last edited:

Dannyboy

Veteran Member
Joined
May 25, 2013
Location
Mb
TDI
2014
And if anybody needs... I've got the oem bearings, slip rings, brushes, regulators and etc for a good bit less than mainiac motors.
Now you tell me ;)
I rebuilt my touareg alternator in December and used manic parts. They shipped each part individually :rolleyes: which ended up costing more in taxes, fees and shipping than what the parts themselves cost.
 

Mozambiquer

Vendor , w/Business number
Joined
Mar 21, 2015
Location
Versailles Missouri
TDI
2004 VW Touareg V10 TDI, 2012 Audi Q7 V6 TDI, 1998 VW Jetta TDI. 1982 VW Rabbit pickup, 2001 VW Jetta TDI, 2005 VW Passat wagon TDI X3, 2001 VW golf TDI, 1980 VW rabbit pickup,
Now you tell me ;)
I rebuilt my touareg alternator in December and used manic parts. They shipped each part individually :rolleyes: which ended up costing more in taxes, fees and shipping than what the parts themselves cost.
I've been on here several years... 😁
Next time you know then.
 

TheKid760

Member
Joined
Mar 1, 2012
Location
PNW
TDI
2003 MK4 Jetta Wagon
Update: 280k miles, alternator slow to get up to voltage, after start it lingers low 12v then slowly as engine rpms and rpms increase it would get to 13.5.

I pulled it and replaced the brushes, working perfectly now.
 

Mozambiquer

Vendor , w/Business number
Joined
Mar 21, 2015
Location
Versailles Missouri
TDI
2004 VW Touareg V10 TDI, 2012 Audi Q7 V6 TDI, 1998 VW Jetta TDI. 1982 VW Rabbit pickup, 2001 VW Jetta TDI, 2005 VW Passat wagon TDI X3, 2001 VW golf TDI, 1980 VW rabbit pickup,
Brushes are almost gone and the slip rings are pretty worn too. I bought it as a core so I really don't care much. Good alternator rebuild how-to maybe?
 
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