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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 July 31st, 2012, 07:54   #1
Looney2uner
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Default 2001 ALH Battery Drain Found!

My 2001 Jetta TDI with 420K Km was draining the battery completely overnight, even with a charger on it showing approx. 3A going into the battery. I bought a $60 DC clamp milliammeter from eBay (model SE02, which died after a week, but showed a 5A drain while it worked). Pulling all the fuses did not stop the drain. I now suspected the alternator diodes (booster cables were reversed when jumping another car, d'oh!)

It dawned on me (at dawn) that a 5A drain equates to 60 Watts of heating going on somewhere. This morning, cold engine, warm alternator = problem located.
An all new 120A unit with new clutch pulley installed (from eBay seller california_alternator_starter, $144) will be going into my favorite car ever.
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Old July 31st, 2012, 08:09   #2
whitedog
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I like it. Sometimes we need to throw away the electronics and use our hands and brains to find problems. I have done the same thing finding high pressure leaks on hydraulic systems. A cold machine with a hot spot points right where the leak is.
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Old July 31st, 2012, 19:04   #3
Gil
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Just wondering.
Is it possible to replace the bad diode or diodes.
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Old July 31st, 2012, 19:06   #4
GenMan
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Quote:
Originally Posted by Looney2uner View Post
My 2001 Jetta TDI with 420K Km was draining the battery completely overnight, even with a charger on it showing approx. 3A going into the battery. I bought a $60 DC clamp milliammeter from eBay (model SE02, which died after a week, but showed a 5A drain while it worked). Pulling all the fuses did not stop the drain. I now suspected the alternator diodes (booster cables were reversed when jumping another car, d'oh!)

It dawned on me (at dawn) that a 5A drain equates to 60 Watts of heating going on somewhere. This morning, cold engine, warm alternator = problem located.
An all new 120A unit with new clutch pulley installed (from eBay seller california_alternator_starter, $144) will be going into my favorite car ever.

Good job, love it...
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Old August 1st, 2012, 05:49   #5
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Quote:
Originally Posted by Gil View Post
Just wondering.
Is it possible to replace the bad diode or diodes.
Yes, you can buy the voltage regulator assembly separately. But, in my case, it had 420,000 km on it (brushes and slip rings near the end of their life?) and the clutch pulley was seized also. So I would have had to buy the clutch pulley removal tool also. For me, easier this way.
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Old August 1st, 2012, 06:05   #6
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I have no idea what Amperage the original alternator was rated at, but I had the choice of buying a 90, 120, 140, and even a 170 Amp replacement. If they're all in the same sized housing, what is the difference between them? Thicker windings, brushes?? Since the internal fan cannot be up-sized much, the high-Amp ones must really get hot at full output.
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Old August 1st, 2012, 13:39   #7
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UPDATE

Uh, oh. This morning I did my touchy-feely test on my alternator and it was COLD! My original, hopefully correct, diagnosis was that my battery drain was through bad diodes in the alternator. Today the car started like it had a fresh battery that did not drain overnight.

So, my question to all you experts out there is: Can a bad alternator/diodes be intermittent?

I've had this problem for months and there were occasions when the car started the next day without being on a charger. The new, replacement alternator is already on it's way to me, so it will be installed regardless of what's causing the problem. I can't think of anything that would drain the battery and also keep the alternator nice 'n warm other than bad diodes.
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Old August 1st, 2012, 13:58   #8
dieselfuel
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Bad solder joint....?
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Old August 1st, 2012, 14:05   #9
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I assume these alternators have brushes if so these could be worn or have a buildup of carbon that arc but only in certain positions? Just a theory.

I really like the hands on diagnosis.
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Old August 1st, 2012, 14:33   #10
03Springer
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Here is the thread on replacing the voltage regulator with part number. Having worked on avionics on military aircraft for 30+ years all I can say is one minute it is working fine and the next it isn't. That is electronics, if it gets too hot or cold, solder joints open, components are affected etc. You won't have to pull the alt if you replace your regulator but if the alt has more than 150K on it then it's cheap insurance to replace it in the comfort of your driveway/garage as opposed to leaving you stranded on the side of the road when it's raining. My .02 cents!

http://forums.tdiclub.com/showthread...or+part+number
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Old August 1st, 2012, 17:51   #11
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Quote:
Originally Posted by whitedog View Post
... Sometimes we need to throw away the electronics and use our hands and brains to find problems. I have done the same thing finding high pressure leaks on hydraulic systems.

PLEASE tell me that you don't actually use your hands to locate high pressure hydraulic leaks! That action can kill you!
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Old August 1st, 2012, 19:19   #12
Looney2uner
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Yah, I knew the voltage regulator could be changed and solve a bad diode problem, but with over 420,000,000,000 mm on the odometer combined with a seized pulley, it would not make sense.
The intermittency (is that a word?) could indeed indicate either a loose solder joint or a cruddy spot on the commutator where an equally cruddy worn brush happened to rest when the engine stopped. I just hope to heck that it's not some mystery stuck relay somewhere. The seized pulley alone is reason enough to replace the whole thing, considering the high millimeterage on the unit.
Of course I'll comment when the job is done. Thanks for all you guys' input.
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Old August 1st, 2012, 19:45   #13
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Lug nut....I've seen someone who had hydraulic oil from a high pressure fitting failure penatrate his finger. It was a very small entry wound that could easily be brushed aside but luckily we new the damage this could cause. The emergancy room basically opened his finger up like a fillet to clean out the tissue damage. It is a very serious injury that can cause amputations or even death as you said. Back on topic, We've had the same issue and fix in the past. I think you made the right call on replacing instead of patching for what it's worth
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Old August 1st, 2012, 22:35   #14
whitedog
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Quote:
Originally Posted by Lug_Nut View Post

PLEASE tell me that you don't actually use your hands to locate high pressure hydraulic leaks! That action can kill you!
Not external leaks. Internal leaks.

In other words, not OOG leaks (Oil On Ground)

but rather OLI leaks (Oil Leaking Inside)

You are right though. If oil is leaking out of a high pressure hydraulic system, don't use your hands to find the leak.
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Old August 2nd, 2012, 16:10   #15
climbtheplanet
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Quote:
Originally Posted by Looney2uner View Post
I have no idea what Amperage the original alternator was rated at, but I had the choice of buying a 90, 120, 140, and even a 170 Amp replacement.
All of my research over the past few days has found that you are correct in buying the 120A. Took mine out yesterday and it was the OEM part from 2001 and is 120A.
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