2012 MK6 Jetta Alternator Clutch Pulley

[LindseyNicole]

Hey everyone, I'm trying to diagnose an issue with the alternator.

The battery light started turning on and off, so I immediately take it to AutoZone. They tell me the alternator is registering as "bad". I get the car home, take the serpentine belt off and see that the clutch pulley is moving the alternator fan in both directions. It is important to note that the belt didn't have any give (at all) when applying pressure (super tight). Prior to this, the serpentine belt was breaking every 3 months or so.

Could it be that I tightened the belt too tight and it wore the bearings out on the clutch pulley? Should I check for any other damages to the pulley system?

Any advice is much appreciated.

Thanks!

 

[2004LB7]

I doubt the tightness of the belt would cause that. The bearings inside the alternator would be going bad too if that was the case.

What you describe is the normal failure mode for the pulley clutch so I wouldn't worry too much about something you did. But... That shouldn't cause the alternator to read as bad on the tester. You probably either need to have the alternator rebuilt or replaced and not just the pulley

PS: I have two cousins that are sisters, one named Lindsey and the other is Nicole

 

[LindseyNicole]

I was thinking the alternator was reading as bad because it wasn't getting proper power amperage from the faulty pulley clutch(?). When the serpentine belt initially broke, autozone said it was the alternator. It was the serpentine belt. Once I changed the belt the alternator reading was within normal range.

My mother was a fan of the two first names thing back in the day. My other two siblings have two first names too. LOL

 

[2004LB7]

From the way you describe it, it sounds like the pulley clutch was locked up and not freewheeling in the backwards direction. This is normal failure mode for the clutch and doesn't stop the alternator or hurt it. But it is hard on the belt & tensioner and would explain the reason for the breakage.

 

[LindseyNicole]

Okay, sweet. I'm going to order a new clutch pulley and install it. Hopefully, it isn't too much of a hassle.

 

[Mozambiquer]

Okay, sweet. I'm going to order a new clutch pulley and install it. Hopefully, it isn't too much of a hassle.

Just make sure any clutch pulley you get is the oem one. The aftermarket ones fail very quickly and put you right back in the same spot.
But with the light coming on, unless the pulley is failed where it is freewheeling, its likely that the failed pulley has killed the alternator.
Those have the Bosch alternator still and the brushes can be fairly easily checked by pulling the regulator off the back. Just pull the cover off (one Phillips screw and the battery cable and the two nuts under it) then three screws for the regulator and it slides right out. Check for short brushes and for grooves in the slip rings.

 

[LindseyNicole]

It is freewheeling.

 

[2004LB7]

If it's freewheeling both ways that would explain why it would fail the test

The pulley is not too hard to change but does require a special spline tool to remove

 

[Tdijarhead]

Here is a you tube video by one of the very knowledgeable members here on this forum on changing that pesky pulley on a 2013.

 

[LindseyNicole]

Thank you guys so much!!