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Discussion Starter · #1 ·
I have a T2 V10TDI. My wife stopped at the gas station and it did not start anymore without jump start help (she pumped Diesel, we have 3 Diesel cars and no gasoline one). I charged the battery at home and it started but I noted the needle of the Voltmeter on the dash is jumping between 13V and 14V (previously was 14V spot on as far as I remember). However, no "Alternator failure" warning light showed up on the dash. I also noted the engine does not idle as smooth as it used to.

Is there any guide here to determine if alternator is dead? Are there any measuring blocks I could use vag-com to monitor charging voltage? I checked 01 ECU and 09 CECM modules, but I have not found anything directly related to alternator voltage. Group 7 Field 0 shows System battery voltage and it was going between 12.45 and 13.05.
 

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Sounds like it's time for new batteries...I just went through something like that on my 2008 V10. Replaced both batteries as they were original and past their life expectancy.

Also I always keep my v10's on a battery tender when ever possible. I have yet to have an issue on my 04 v10 doing this...
 

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Someone else is having issues on their V10 generator [VW's name for the V10 alternator] too.

It might be the clutch that is part of the generator/alternator drive coupling.
 

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It's because there is no warning light that I'm wondering [possibly in my naivety] if it is that clutch.

There are others on here with a far, far better understanding in this area - I wish they'd bloody well chime in for your sake AND mine!!
 

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Clutch or no clutch - if the alternator does not charge, the light should be on. Unless this light is as good as emission certification...
Generally the easiest way to check an alternator is to start the car and disconnect the battery, car should still run off the alternator. Not certain if this works in a two battery situation.
 

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Generally the easiest way to check an alternator is to start the car and disconnect the battery, car should still run off the alternator. Not certain if this works in a two battery situation.
Yes, but, if the alternator field has current, a magnetic field will be generated.

You could start vehicle and take a ferrous object, like a wrench, and see if sticks to the rear of the alternator. If it does not stick, then the alternator "field" is not being generated. Trouble shoot further.

The battery on a T2 is hard to get at to remove a cable while the engine is running, and DANGEROUS!! Main rule of safety, NO SPARKS AT THE BATTERY!!

Under the right set of circumstances, the battery under the seat can become a good sized BOMB!!

Consult the Self Study Programs on how the charging system works before trouble shooting and working on the start/charge system.

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NEVER EVER disconnect the battery with the engine running. The alternator is charging the battery by putting out a higher voltage than the battery. When you disconnect the battery, the alternator and other electronic components on the system will see large voltage spikes that can cause serious damage. This is called load dump. A very costly mistake to make.
 
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NEVER EVER disconnect the battery with the engine running. The alternator is charging the battery by putting out a higher voltage than the battery. When you disconnect the battery, the alternator and other electronic components on the system will see large voltage spikes that can cause serious damage. This is called load dump. A very costly mistake to make.
Been doing it for years and never have had a problem disconnecting the negative cable or any electrical issues either after. Doubt the voltage spike you indicate is that substantive or the danger of a bomb per other response.
 

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Hi, do you know the off gas of a battery under charge is hydrogen?

Just for the heck of it, Google battery explosions and see what you find.

If you still think there is no danger, carry on. You could become a Darwin Award winner.

By the way, ever hear of an amp clamp?

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Been doing it for years and never have had a problem disconnecting the negative cable or any electrical issues either after. Doubt the voltage spike you indicate is that substantive or the danger of a bomb per other response.
Just because you have gotten away with this procedure many times does not make it correct or safe.

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Yes, but, if the alternator field has current, a magnetic field will be generated.

You could start vehicle and take a ferrous object, like a wrench, and see if sticks to the rear of the alternator. If it does not stick, then the alternator "field" is not being generated. Trouble shoot further.

The battery on a T2 is hard to get at to remove a cable while the engine is running, and DANGEROUS!! Main rule of safety, NO SPARKS AT THE BATTERY!!

Under the right set of circumstances, the battery under the seat can become a good sized BOMB!!

Consult the Self Study Programs on how the charging system works before trouble shooting and working on the start/charge system.

****
Magnetic field generation doesn't mean the alternator output is sufficient. A large amount of voltage is required to run the electronics of the car even at idle. Think you are overstating the danger of the battery unless you are venting it into the container. Yes vented vapor from the battery could ignite however if you have build up that is a problem. Should be none. Yeah the under seat is a pain however but not difficult. I loosen the negative cable prior to starting and get no sparks when removed, car should keep running. When it does I just shut off and reconnect negative cable. Never have had a problem with any of my three VWs- Tiguan, GTI and T1. Just like everything about the car over engineered and understand how the charging system works per the study guide which is mostly related to two battery systems.
 

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scubacruiser is spot on. Should never run engine without a battery load. Usually and instantly blows the bridge diodes in the alternator. that is why boat battery switches (for example) are designed to switch batteries from posit one to both to posit two, never interrupting to ensure a battery is connected at all times. best method of checking an alternator, take a reading of battery voltage with motor not running, ie 12.2 volts, start motor, check reading... it should jump up to near 14.2 volts depending on how low the battery is....but it should increase.
 

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I have a T2 V10TDI. My wife stopped at the gas station and it did not start anymore without jump start help (she pumped Diesel, we have 3 Diesel cars and no gasoline one). I charged the battery at home and it started but I noted the needle of the Voltmeter on the dash is jumping between 13V and 14V (previously was 14V spot on as far as I remember). However, no "Alternator failure" warning light showed up on the dash. I also noted the engine does not idle as smooth as it used to.

Is there any guide here to determine if alternator is dead? Are there any measuring blocks I could use vag-com to monitor charging voltage? I checked 01 ECU and 09 CECM modules, but I have not found anything directly related to alternator voltage. Group 7 Field 0 shows System battery voltage and it was going between 12.45 and 13.05.
Seeing the V10 has dual batteries, could the problem lie with the Battery Isolation relay which is located with the front battery under the left seat. I have attached the Self Study Program for the Battery System which may help your diagnosis. See Diagram on Page 16 "Charging Circuit Relay". As this controls power to and from the rear battery.

Also, have you tried activating the "emergency start" option as detailed in the attached document. I believe you turn the key to the left and hold for 3 seconds then turn to the right and start normally. This shifts the "start" load from the rear battery to the front. Must be done with key, not keyless start.


Beyond that I can offer much as my car is a single battery only and I haven't experienced this.

Stuart...
 

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Magnetic field generation doesn't mean the alternator output is sufficient. A large amount of voltage is required to run the electronics of the car even at idle. Think you are overstating the danger of the battery unless you are venting it into the container. Yes vented vapor from the battery could ignite however if you have build up that is a problem. Should be none. Yeah the under seat is a pain however but not difficult. I loosen the negative cable prior to starting and get no sparks when removed, car should keep running. When it does I just shut off and reconnect negative cable. Never have had a problem with any of my three VWs- Tiguan, GTI and T1. Just like everything about the car over engineered and understand how the charging system works per the study guide which is mostly related to two battery systems.
Perhaps, but using a wrench, or other, is a quick and easy way to check if the alternator field is being energized without disconnecting anything. Then, trouble shoot further.

Having the alternator only run the vehicle is inconclusive. If you have an amp clamp with a multimeter, then you can properly start, or continue, trouble shooting without any disconnects.

Having a proper AVR test will tell you everything.

Overstating the danger??

Like is said, Google battery explosions and draw your own conclusions.

****
 

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Perhaps, but using a wrench, or other, is a quick and easy way to check if the alternator field is being energized without disconnecting anything. Then, trouble shoot further.

Having the alternator only run the vehicle is inconclusive. If you have an amp clamp with a multimeter, then you can properly start, or continue, trouble shooting without any disconnects.

Having a proper AVR test will tell you everything.

Overstating the danger??

Like is said, Google battery explosions and draw your own conclusions.

****
Won't disagree that hydrogen vapor is explosive and easily ignited - Hindenberg.

A poorly maintained battery with low electrolytes could allow arcing between plates and ignite gas internal to the battery. Bet most insurance claims related to explosions are poor battery conditions or defect. Given the number of folks that incorrectly boost a dead battery causing sparks just don't hear about explosions galore.

One thing is conclusive. The car will die if the alternator is shot. It takes a hell of a lot of voltage output to run the car at idle with no accessories on. Modern cars are voltage hogs.

As with any problem with a car proper diagnostic equipment beats shortcuts which are not conclusive. Alternator could be fine but related relay could be shot. Pretty easy to check relays. If my voltage gauge reads less than 14v when running there is a problem. Generally with my cars, has always ended up the battery. Maybe lucky but haven't replaced an alternator since the 68 mustang I had in high school. Did have to replace the generator on the bug I drove in college. There is a robust rebuilt alternator industry so they do go bad, however have known folks to replace only to find out battery the culprit.
 

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Discussion Starter · #19 ·
Off topic comment: the hydrogen fumes in Touareg are drained out if I understand correctly the tubes connected to the batteries.

Back to the topic: I got extended warranty and the car is at the dealership. I am still not convinced it is alternator that's dead, but I'll let them figure it out.
 

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Off topic comment: the hydrogen fumes in Touareg are drained out if I understand correctly the tubes connected to the batteries.

Back to the topic: I got extended warranty and the car is at the dealership. I am still not convinced it is alternator that's dead, but I'll let them figure it out.
Yes there is a vent line that connects to battery and dumps vapor out the bottom of battery holder to underneath the car.
 
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