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Go Back   TDIClub Forums > TDI Model Specific Discussions Areas > VW MKIV-A4 TDIs (VE and PD)

VW MKIV-A4 TDIs (VE and PD) This is a general discussion about A4/MkIV Jetta (99.5-~2005), Golf(99.5-2006), and New Beetle(98-2006). Both VE and PD engines are covered here.

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Old January 15th, 2020, 13:26   #1
spreadpanic
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Default ALH intermittent battery light flashing. Several tests done, yet still undiagnosed.

Hello all,


Two weeks ago, my battery light started intermittently flashing. The flashes have started getting more frequent, and longer.


Multimeter to the battery says 12.5v with the engine off. When engine is idling, ~14.5v. When the engine was reved to around 2000 rpms, fluctuated between high 13s and low 14s, even while the battery light flashed several times.


There is a little bit of squealing around the serpentine area. Tensioner looks a little jumpy, but not as bad as I've seen in some videos.


After removing the serpentine belt, I found all of the pulleys to spin freely, or without much resistance, in both directions. There is a little bit of bearing noise in the tensioner pulley, but still a smooth spin.


As for the alternator pulley, it spins only counterclockwise when I put a screwdriver into the housing. I am met with a little bit of resistance, enough so it stops spinning as soon as I remove my hand.


Inside the car, I checked the fuses with the battery symbol, none were blown. Electrical is not my strength.


Is there anywhere else I should start looking into? Could it just be a computer/sensor issue?
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Old January 15th, 2020, 13:28   #2
WildChild80
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Almost guarantee it's the clutch on the alternator
Similar issue and swapped the pulley and all is well
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Old January 16th, 2020, 06:23   #3
mauricioezequiel
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How many miles has the alternator pulley?
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Old January 16th, 2020, 06:38   #4
steve6
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In for alternator clutched pulley as well

Funny story, I had a 2003 jetta, and I had the alt light start flashing, I was on the highway so I just kept driving, about 90 minutes later it turned off. I didn't do anything about it, about 6 months later it flashed again for a few minutes randomly, stopped and life went on. It did that every so often but never totally failed. I drove that car for over 6 years and up to almost 600,000 kms, never did change the alternator.
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Old January 16th, 2020, 06:45   #5
Genesis
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Yeah, the bad news is that one day you may have a load of fun when the pulley grenades and takes out things under there. In the worst case some piece of the carnage gets behind the timing belt cover and then you're hosed.

The other alternative is that it will fail locked up hard, in which case the shock on the tensioner will be destroyed quite quickly. That's cheaper than the other disaster by a lot, but still kind of a pain in the neck.
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Old January 16th, 2020, 08:17   #6
mauricioezequiel
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Quote:
Originally Posted by Genesis View Post
Yeah, the bad news is that one day you may have a load of fun when the pulley grenades and takes out things under there. In the worst case some piece of the carnage gets behind the timing belt cover and then you're hosed.

Mine fell apart when I changed it, the only symptom was some flashes of the battery light on the dashboard when driving on the highway; and also looked quite healthy when was still attached to the alt.
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Old January 16th, 2020, 08:22   #7
WildChild80
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mine made a chirping sound and and the lights would dim a little

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Old January 16th, 2020, 08:59   #8
spreadpanic
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Quote:
Originally Posted by mauricioezequiel View Post
How many miles has the alternator pulley?

I put in a Bosch reman 4 years ago, but have been living out of the country half the time, so probably only around 20,000 miles.


Based on everyone's feedback, yes, I think the pulley is the next logical step. I'm just confused why I am still getting a solid 14V to the battery at 2000 rpm, even though the battery light is flashing. I'm not good with electrical, but the constant 14ish feels like that would indicate the alt is doing its job smoothly?


It's actually still under warranty, but honestly I'd rather spend $50 on a spline tool and pulley, be done with it (hopefully) in 20 minutes, than going through the process of yanking the whole unit. I've already had to do several other things to the car this month, kinda out of time for it!
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Old January 16th, 2020, 09:20   #9
Vince Waldon
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Digital multimeters have a lag in their response and are also not good at catching brief changes, whereas the alternator warning system flags them at the speed of light.
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Old January 16th, 2020, 09:45   #10
Rrusse11
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Quote:
Originally Posted by spreadpanic View Post
I put in a Bosch reman 4 years ago, but have been living out of the country half the time, so probably only around 20,000 miles.


Based on everyone's feedback, yes, I think the pulley is the next logical step. I'm just confused why I am still getting a solid 14V to the battery at 2000 rpm, even though the battery light is flashing. I'm not good with electrical, but the constant 14ish feels like that would indicate the alt is doing its job smoothly?


It's actually still under warranty, but honestly I'd rather spend $50 on a spline tool and pulley, be done with it (hopefully) in 20 minutes, than going through the process of yanking the whole unit. I've already had to do several other things to the car this month, kinda out of time for it!

My serpentine belt was showing signs of wear, spotted by my sharp eyed
guru. No symptons, yet, but investigation of the issue and my pulley was
seized. Even my pros wouldn't attempt to do it in place.
So about 3 hours total to get the alternator out and on the bench and re-installed.

Good luck with your 20 minute fix.
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Old January 16th, 2020, 10:01   #11
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There was talk of metal nerd making one you could use in place but it just seems like a bad idea, I've had a few that the triple square bit needed a little tapping to get it seated...hard to do in an already cramped space

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Old January 16th, 2020, 10:16   #12
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If for whatever reason changing the pulley doesn't fix the problem, next place to look would be the voltage regulator. My light started flashing randomly one day, then almost immediately the cluster started going nuts (Speedo and tach fluctuating wildly, multiple lights flashing). Pulled over and checked voltage, was producing 18 volts at idle. Unplugged it and fiddled with it and somehow got it to stop, only producing like 12.9 volts so I could limp it home on back roads while monitoring voltage from obd. Pulled into the driveway, popped the hood to do more investigation, and the alternator burst into flames before my eyes.

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Old January 16th, 2020, 12:10   #13
BobnOH
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I'd start with all the big wire connects,battery, alternator, whatever feeds the cluster/ignition.
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Old January 16th, 2020, 12:19   #14
csstevej
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It can be done in the car, I’ve done several of them.
I’ve yet had to pull the alt just to change the alt pulley.
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Old January 16th, 2020, 12:39   #15
steve6
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Quote:
Originally Posted by Rrusse11 View Post
So about 3 hours total to get the alternator out and on the bench and re-installed.
3 hours is a lot.. I've changed them in under an hour. A/C compressor drop, Fan removal, remove belt, unbolt tensioner and then alternator, a few wires, wiggles on out.

Last edited by steve6; January 16th, 2020 at 16:36.
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