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Old June 28th, 2010, 10:48   #1
E28Don
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Join Date: Dec 2006
Location: Kalamazoo, Michigan
Default Fusible Link, Battery Drain, Alternator? on '02 Jetta

I've done some searching here, and think that I have a course of action in my troubleshooting, but am looking for confirmation before I get too heavy into disassembly.

02 Jetta TDI, 200k miles, pretty much out of the blue, doesn't start after sitting overnight. Jumpstarts fine, starts again fine after running, but if it sits for a few hours while at work, needs jumped again. Took her to Advance Auto for electrical system diagnosis, report comes back: battery fine, charging system fine, but there's a 3.5A drain somewhere.

Using my trusty ammeter, I find the drain in the fusible link box on top of the battery. It's the heavy black wire, closest to the centerline of the car, and does show a 3.5A current with the battery hooked up (ammeter placed in-line between disconnected wire and fusible link terminal). With everything disconnected, that same wire shows 660 ohms to ground, fwiw. I believe that this wire goes to the alternator, and from reading here, this stray current could be due to a bad alternator diode, or frayed insulation on the wire. I'm inclined to think the diode is more likely, as a simple grounding of the wire would show a lot less resistance.

Other factors?: Radio has had a lot of static, esp. on AM; tried grounding radio chassis, to no effect, and removed extra ground strap. Glow plugs replaced several weeks ago. Battery is only six months old. Voltage across battery with car idling, 14.25V.

Proposed Course of Action: Trace cable from fusible link box to alternator. If nothing found there, assume it's the alternator and replace.

Am I on the right track?

Thanks in advance for your input.

Don
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Old June 28th, 2010, 11:54   #2
kbrenny
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Location: Sachse, Texas
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Sounds like the same exact problem I had with just a slightly lower draw (2 amp). I checked the cable with no grounding issues and then replaced the alternator.

That fixed my problem and the car can now sit for days and starts fine, before it could only sit for 24 hours or it would need a jump start.

My alternator was original with only 130k miles on it.

Before that I had a monsoon amp that was not turning off when the car was turned off and it drained the battery overnight.
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Old July 1st, 2010, 09:16   #3
E28Don
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Okay, now. Did a little more looking.

My 02 TDI has automatic transmission, and a closer look at alt shows it to be a 90A unit with a removable regulator.

Is the diode pack associated with the regulator, a separate replaceable module, or is it integral to the alternator, necessitating R&R of the alternator itself?

Thanks.
Don
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Old July 2nd, 2010, 12:35   #4
kbrenny
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I believe there is a post somewhere on here about replacing just the regulator. I dont recall where it was but I think it can be done, and possibly without removing the alternator from the car.

I was going to go that route but I had the 90 amp and wanted the 120 amp because of the huge stereo system I have. The place I bought my alternator took the 90 amp as a core with no issues and sold me the 120 amp.

the 120 amp was also lower priced than the 90 amp

the 90 amp had to be ordered (5 days) and the 120 amp was in stock

no brainer for my case.
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Old August 29th, 2010, 14:14   #5
B1nky
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Location: Florida
TDI(s): 2000 Bug
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I am hunting down a similar problem in a 2000 TDI Bug. I have the Bentley manual and I see a 3 AMP draw across six circuits on top of the battery. The numbers are
177 A black wire - Generator
176 A Red wire - Vehicle Electrical system relay panel
164 A Black wire with a Red stripe - Coolant Fan Two Speed
and all three fuses
178 - ABS Hydraulic Pump
179 - ABS
180 - Coolant Fan Single
I am having trouble reading the schematics in the manual. But I suspect a common part like the alternator, Cooling Fan (Which I have already disconnected) or the ABS hydraulic pump is the problem. Any other suggestions? Thank you
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Old August 29th, 2010, 18:16   #6
E28Don
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B1nky,
Sorry I don't have a better answer for you, but I never ran this problem "to ground." At least as far as replacing only the regulator. My son, who is driving the car, and may be more stubborn than me, had the alternator replaced. FWIW, it solved the problem.
Don
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Old August 30th, 2010, 13:43   #7
BeeselDietle
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http://forums.tdiclub.com/showthread.php?t=202696
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