NEED HELP. after alternator pulley replacement, alternator doesn't charge???

Hey guys, my 06 tdi jetta had a tensioner rattle so I replaced the alternator pulley. So I put everything back, there is no more tensioner belt rattle, spins super smooth but now I have a battery light ON and the alternator does not charge the battery at all.

I know the alternator isn't charging because I started the car and then took off one of the battery terminals and the car shots off. If the alternator was charging the car would NOT turn of if you do this.

Whats the problem now? Do 06+ Tdi Jettas have any alternator fuse or any other fuse that could be causing the alternator not to charge?

I'm thinking about taking it off AGAIN and inspecting the brushes on the alternator but before I do that I figure I ask and see if anyone has any input.

Thanks

You almost-certainly destroyed the diode pack in the alternator doing that.

You NEVER, EVER unload an alternator by removing the battery terminals while the car is running. The back-emf will usually exceed the diode reverse ratings and destroy them instantly.

I believe the brush and regulator/rectifier assembly on these can be reasonably-easily replaced, which is the good news.. I guess.

Wasn't charging before I did that. Even before I took one terminal off, the battery was only reading 11.7 volts with the car running.

Do you know if there is a fuse or anything else that could be causing it not to charge other then the regulator/brush assembly which I will replace next?

I believe there is a fuse on the ALH cars at least, and I suspect there is one on yours too. Look at the block at the battery or trace the alternator positive wire and you should find it.

Yea because right after I took the alternator out, I accidentally connect the positive alternator battery (the thick wire) to the ground and caused just a little bit of sparking.

I was trying to fix it without disconnecting the battery so I don't reset everything in my car.

Uh, that's not good. Don't do that. I assume you blew a fuse but if not you may have damaged the harness to the alternator.

Ok yea i found the fuse, its a really fat looking fuse thats 200A and its blown. Thats good, I def didn't want to remove the alternator again.

For anyone reading this in the future the fuse box is located on the right/drive side of the engine bay, and these big fuses are on the front side of the box, not inside the box. And I guess they are called "strip fuse". Now I only need to find one.

You may still be in for removing the alternator again -- running the alternator with it disconnected (and a blown fuse is the same thing) from the battery runs the same risk of trashing the diodes. See if it works but don't be terribly surprised if it doesn't.

I just soldered the fuse together until I get a new one and the car is fine no battery light and voltage is 14v

These fuses look weird so I don't think I'll find them at local parts store so I might have to order it online or call up VW dealer.

Uh, don't do that. If you have a short with no fuse you're gonna get a fire.

There's more than enough energy in the battery to burn the car to ash. You've just defeated the very reason there's a fuse -- to prevent burning the car up.

Yea I know but there shouldn't be a short between the alternator and the engine. I only soldered in a skinny wire between two sides of the fuse, the thin wire will still burn away if somehow I did get a short.

I'll go to VW tomorrow and get one so it won't be on there for long.

supak111 said:

I know the alternator isn't charging because I started the car and then took off one of the battery terminals and the car shots off. If the alternator was charging the car would NOT turn of if you do this.
Thanks

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supak111 said:

Yea because right after I took the alternator out, I accidentally connect the positive alternator battery (the thick wire) to the ground and caused just a little bit of sparking.

I was trying to fix it without disconnecting the battery so I don't reset everything in my car.

Click to expand...

supak111 said:

I just soldered the fuse together until I get a new one and the car is fine no battery light and voltage is 14v

These fuses look weird so I don't think I'll find them at local parts store so I might have to order it online or call up VW dealer.

Click to expand...

Genesis said:

Uh, don't do that. If you have a short with no fuse you're gonna get a fire.

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Hahaha, man.. This guy is on that next level of DIY'ers. Natural Selection.

Why did you not disconnect the battery when working with the alternator disconnected?

Why did you not think there was a problem after the giant several hundred amp spark occurred?

The whole "removal of the battery cable" trick is OLD OLD OLD OLD thinking. Are you 95 years old? That may have been ok in 1962 when the cars still had 8A generators and no ECU/ECM's to destroy! lol

Lol no I'm 29. I was too lazy and too cold to look for a multimeter. Its 10 degrees here, couldn't feel my fingers. Thank god its fixed for now.

PS and most cars don't have a fuse on the positive alternator wire so a few sparks shouldn't burn anything out.

supak111 said:

I just soldered the fuse together until I get a new one and the car is fine no battery light and voltage is 14v

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Better get on that quick, before she burns down! lol

Its just a Jetta anyways lol