2000 Beetle alternator wiring question

[Go Time Racing]

I have a no charge issue with my 2000 Beetle 2.0 litre. I had the alternator tested and it tests good. I have no wiring / fuse issues at the fuse box. I only show battery voltage at the cable on the back of the alternator. I am wondering what the connector plugged into the alternator is for. There are two wires in the connector. One shows battery voltage and the other shows little to no voltage. Do these go to the ECU or maybe ignition switch? I cannot locate any wiring diagrams that illustrate this connector.

On a side note... where in the world is the ECU located?

Thanks in advance.

Mike

[VWBubba]

It may sound silly but when you turn the key, does the battery light come on ? If not your fault could be there as the bulb is part of the circuit.

[Go Time Racing]

Originally Posted by VWBubba

It may sound silly but when you turn the key, does the battery light come on ? If not your fault could be there as the bulb is part of the circuit.

Steve, Yes the battery light comes on when the key is turned on and then goes off when the car starts. Thanks for the help.

[VWBubba]

Then I am missing something here, if the light comes on, goes off when running and the alternator is showing output, where is the charging problem?

If you find you have a flat battery all the time it could be a dead cell in the battery, if so it will not charge or hold charge. With the engine off test the battery, it should read between 11.5 and 12.5v on average, better still if the battery is fully charged do a voltage drop test. Start the car and check again that there is charge getting to the battery from the alternator, this should be anything up too 14v.

[IndyTom]

Check the wire going from the alternator to the Fuse box on top of the battery. VW used a low quality wire which caused a lot of melted down fuse boxes.

The ECU is located under the left side of the dash inside your car. You have to take the center piece off and then the left plastic piece. I am attaching a PDF from APR that shows how to get to it.

[Go Time Racing]

Originally Posted by VWBubba

Then I am missing something here, if the light comes on, goes off when running and the alternator is showing output, where is the charging problem?

If you find you have a flat battery all the time it could be a dead cell in the battery, if so it will not charge or hold charge. With the engine off test the battery, it should read between 11.5 and 12.5v on average, better still if the battery is fully charged do a voltage drop test. Start the car and check again that there is charge getting to the battery from the alternator, this should be anything up too 14v.

The light goes on and off like it should, and stays off. But, the alternator does not charge. While running, I only have battery voltage (say 12.2v) coming out of the cable at the alternator and at the battery.

UPDATE: I went out and did a voltage drop test which tests OK both positive and negative circuits. Interesting though is that when I first start the car, the voltage runs up to around 13.6v for around 5 seconds, and then slowly goes back down to under 12.2v. It's like it is charging at initial start-up, but then stops.

I'm still haven't figured out where the two wires that are in the connector at the alternator run to. I'm guessing one goes to the bulb at the dash, and the other to ECU-Ignition switch?

I had the alternator tested at O'Reilleys Auto Parts last night and they said it was putting out proper amperage. Could it be that they just test it for a second or so, and this one craps out after running for more time?

My next step... deciding whether to go with a slug or bird-shot.

[Go Time Racing]

Originally Posted by IndyTom

Check the wire going from the alternator to the Fuse box on top of the battery. VW used a low quality wire which caused a lot of melted down fuse boxes.

The ECU is located under the left side of the dash inside your car. You have to take the center piece off and then the left plastic piece. I am attaching a PDF from APR that shows how to get to it.

Thanks for the response Indy Tom. I checked the wire you mentioned and it is OK. I even ran a jumper cable from the back of the alternator to the positive terminal to see if that would make a difference. It did not.

[IndyTom]

Did you have the battery tested? Perhaps it just can't accept the charge coming from the alternator. Did you check the fuses on top of the battery?

[Go Time Racing]

Originally Posted by IndyTom

Did you have the battery tested? Perhaps it just can't accept the charge coming from the alternator. Did you check the fuses on top of the battery?

The fuses are all good on top of battery and show no signs of heat. The battery tests good, but for grins I already tried another known good battery with the same results.

[VWBubba]

Not sure about these NBs as they are new to me but I know some vehicles have a separate regulator that allows more output on start up especially in winter when all the goodies like heated seats, demist, heaters and so-on are turned on. My thoughts are heading towards alternator fault or separate regulator if it has one. any possibility you could 'borrow' a good alternator to try before you buy?

When they tested the alternator did they test under full load, i.e everything electrical that is possible turned on?

[IndyTom]

If the battery box is fine and the wire from the alternator to the battery box is in good shape and the battery tests out okay then I would say it is the alternator regardless what the tests show. Perhaps it isn't the alternator directly but the voltage regulator which I don't think will show on the test that autozone or whoever performed.

[IndyTom]

I found this answer to a similar problem which MORAV one of our helpful members on the ORG discussed on the Vortex:

As complicated as VW has made the entire elctrical system on their cars, the charging system is the simplest of simple. The alternator puts out the charge, the battery receives it. Via one direct path through the main fuse box which sits atop the battery. If the alternator is not charging the battery it will (should) trigger the "generator" warning light on your instrument cluster, the warning light many incorrectly refer to as the "battery" light. If the battery is bad, you will not get a light (and no codes). You say both have been bench tested, out of your Bug. The normal way to test an alternator is a load test, while in the vehicle, with the engine running.

The ONLY things that can fail are
1) the Alternator
2) the Voltage Regulator (an integral part of the Alternator which limits the voltage going to the battery)
3) the Battery
4) the wiring that delivers the current from point "A" (alternator), to point "B" (battery), including the main fuse block atop the battery

No DTCs (Diagnostic Trouble Codes) will be thrown with the failure of any of these components.

For the moment lets assume you are correct in your diagnosis that the Alternator/Voltage Regulator, and the Battery are good. This leaves only a problem with delivery. The components of the delivery system are
1) Alternator to body ground, accomplished through the mounting
2) Battery to body ground, via battery cable, check both ends for CLEAN and TIGHT, and integrity of cable
3) 25.0 mm² (+/- #3) Black Cable from Alternator to Battery Box Fuse Position [S177], check both ends for CLEAN and TIGHT, and check for integrity of cable (this is a problematic lead in the NB)
4) Fuse (Position [S177]), amperage determined by alternator size
5) Fuse Block (this is also problematic, subject to melting, in the NB), check for any visible damage
6)16.0 mm² (+/- #5) Red Cable from Fuse Block to Battery check Battry connect for CLEAN and TIGHT and check for integrity of cable

I would have a look at this link
http://newbeetle.org/forums/question...box-issue.html
then have a close look at your fuse block. If everything looks good, no melting, integrity of all leads good, all connections clean and tight, I would make sure the battery is fully charged and take it to the Corner Parts Store (Advanced AP is a good place), and have your alternator and battery rechecked. Your NB will easily run 20-50 miles on a fully charged Battery, dependent upon what else you have running, e.g. a/c, headlights, etc, even if the Alternator is bad.

I don't spend a lot of time on the Vortex, and don't particularly follow the threads here, I don't check the email that I get p/m notices on very often. I'm always around on "the Org", same user ID. Let me know if I can help furthr.

MORAV