# Alternator Fault



## StormENT (May 11, 2021)

Whilst driving home I had an error pop up on the dash saying, "Alternator Fault: Battery is not being charged".
I was only a few minutes from home so manged to get back just in time as the power steering started to fail as I reached my road.
There were various error massages but most were due to low voltage alerts. 
I had 3 DTC errors under 61) Battery Regulation, all coded 02252. They were "Mechanical Failure", "No Signal/Communication" and "Electrical Fault In Circuit".
I've changed the voltage regulator on the alternator and the belt seems tight enough but I'm still seeing less than 12v when the car is running.
After clearing all errors since the regulator change, only "No Signal/Communication" has returned.

Is there a way to test if this is an electrical issue or I need a new alternator?


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## Hoggy (May 8, 2002)

Hi, Very unusual for an alternator to fail, & as you have replaced the reg recheck the connections at alternator & check the alternator fuse/connections for failure/poor connection. I don't have a MK2 but I would think that fuse is located in the fuse box near battery. Someone may know for sure.
Hoggy.


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## SwissJetPilot (Apr 27, 2014)

This post from the *Ross Tech* forum may help -

https://forums.ross-tech.com/index.php?threads/13952/

When your battery was replaced, was it re-coded? Be aware this is year specific as not all Mk2 TT's have the battery management module.

*FAQ - Battery Replacement and Recoding*
https://www.ttforum.co.uk/forum/viewtop ... &t=1878169


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## StormENT (May 11, 2021)

Hoggy said:


> Hi, Very unusual for an alternator to fail, & as you have replaced the reg recheck the connections at alternator & check the alternator fuse/connections for failure/poor connection. I don't have a MK2 but I would think that fuse is located in the fuse box near battery. Someone may know for sure.
> Hoggy.


Thanks Hoggy,
I did a visual confirmation of all the Solid type fuses under the bonnet and next to the positive terminal of the battery in the boot. I also did a continuity test of every blade fuse I could find in the car but I'm not sure if there are any more hiding somewhere.


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## StormENT (May 11, 2021)

SwissJetPilot said:


> This post from the *Ross Tech* forum may help -
> 
> https://forums.ross-tech.com/index.php?threads/13952/
> 
> ...


Thanks Swiss,
The latest battery was a like for like (Varta 80ah) but I did recode the serial number yesterday and have confirmed that the battery aging has reset back to 100%.

Below is all the data I pulled on Battery Regulation whilst the car was running. I noticed that Exciter Current is at 0A but I'm not sure if this is accurate or just not being reported due to the no communication DTC


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## StormENT (May 11, 2021)

Still having issues tracking down this fault. Does anyone know what the Generator module that can't be communicated with is? Would this be inside the voltage regulator, and if so, should I be able to communicate with it even if the alternator itself is dead?

I found the following wiring diagram and have confirmed all the SA fuses are fine. I guess my next step is checking the LIN bus but I'm not sure how to go about doing that so any pointers would be appreciated.


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## SwissJetPilot (Apr 27, 2014)

The *Alternator* is covered in the two different workshop manuals linked below and discuss both the *Bosch* and *Valeo* manufacturers -

*FAQ - Audi TT (8J) Workshop Manuals & Self Study Programs*
*• Electrical System - RG 27 90 93 94 96 97 - A005TT01320*
*• Electrical Equipment General Information - RG 27 92 94 96 97 - D3E8007DE6D*
https://www.ttforum.co.uk/forum/viewtop ... &t=1833829


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## StormENT (May 11, 2021)

Thanks,
I had taken a look at that but couldn't find any info on the actual electrical systems of the generator. Taking the following for example......










I assume that (3) is the data connection to the voltage regulator. If that's the case then is there any way I can test the cable is doing what it's meant to be doing and that the (newly replaced) regulator is being communicated with?

I suspect it's not but I'm not sure how to confirm this. Is the Lin bus just for diagnostics? Does the J519 control the generator or is it just receiving data? If I have a bad alternator but a good regulator, would I be getting the DTC 02252 No Signal/Communication error? etc.....


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## Wolvez (Jun 22, 2018)

Number 2 in the picture is the big positive cable. Maybe there is corrosion on the alternator mount? Use a ohmmeter to check the resistance between the alternator housing and jumper body ground.


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## Wolvez (Jun 22, 2018)

Check for voltage on the alternator big positive cable and jumper body ground? No voltage? Check the fuse box at the engine bay. SA1 = Alternator inline 175A fuse


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## StormENT (May 11, 2021)

Hi Swiss,
I've looked through the A8L Electrical Components SSP you posted (And since deleted?) It's certainly got me a step in the right direction but I'm coming up against some roadblocks as the A8 electrical addresses seem to differ to the TT.
Do you have a similar document for an 8J?


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## StormENT (May 11, 2021)

Wolvez said:


> Check for voltage on the alternator big positive cable and jumper body ground? No voltage? Check the fuse box at the engine bay. SA1 = Alternator inline 175A fuse


Hi Wolvez,
I can confirm there's voltage on the big positive cable. Looks like battery voltage minus distance loss so nothing being generated at all. All the SA fuses look to be intact and undamaged.


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## SwissJetPilot (Apr 27, 2014)

@ *StormENT* - Yeah, sorry about that. But after I posted it and then read the SSP more in detail, it seemed not to have that much in common with the Mk2 TT alternators, and was a bit too specific to the A8 which is why I deleted the post - to avoid confusion. I also found a 2019 electrical system SSP, but thought it would be too new to be of value.

Unfortunately, the Mk2 TT only had four or five SSPs and none really went into that much detail on the electrical system. You can find them in the link for the *Workshop Manuals*.

Here's the *A3 Electrical System* and *Vehicle Battery* SSPs. See what you think -

View attachment SSP-312-Audi-A3-2004-electrical-system.pdf

View attachment SSP-234-Vehicle-batteries.pdf

Following on *Wolvez's* advice, have you checked the fuseable link on the battery terminal? Someone commented they were having electrical problems and only noticed one was broken under a very close inspection.


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## Wolvez (Jun 22, 2018)

The alternator pulley has a one way clutch, remove the belt to check the one way clutch. Insert a stick or finger inside to hold the fan then try turning the pulley clockwise and counter clockwise. Your alternator pulley could be freewheeling and not actually turning the alternator assembly when the engine is on.


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## MT-V6 (Jan 11, 2015)

Does your can gateway module show any faults? As far as I know the battery regulation and associated linbus is controlled via the gateway directly, unlike other modules which are connected to it via canbus


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## John-H (Jul 13, 2005)

My experience is with Mk1 but usually alternators are pretty simply connected. There's ground through the mounting and engine earth strap (which is OK if the starter works), then there's a big thick cable back to battery positive through a big link fuse. Your regulator module is often the item that is most likely to fail and can be replaced without too much trouble. The rectifier diodes in the alternator windings rarely fail. You can probably shine a torch into the alternator to see movement. You should get around 14V when charging.


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## SwissJetPilot (Apr 27, 2014)

I read in the *Ross Tech Forum* (linked below) that with the Valeo alternator it's possible to get the wrong regulator. Looking at the parts list both Bosch and Valeo seem to have a few different regulator revisions.

I'm not sure it this is directly related to the issue you're experiencing, but may be worth looking into.

*J533 J367 and Generator problem Audi A4, B8, 2.0TDI Multitronic - 2008 Engine CAGA*
https://forums.ross-tech.com/index.php?threads/13952/


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## tttony (Dec 21, 2014)

Up till about 15 years ago we had a shop just a few miles away that just tested and repaired vehicular dynamos, alternators and starter motors. They had electric motors on jigs to spin up dynamos and alternators to test their output. Bearing replacement, brush replacement and even re-windings were their bread and butter. The guys wore filthy workshop coats and had carbon dust and grease on face and hands but provided a great service.

Nowadays nobody seems to have the skill or inclination to do that sort of work. Modern "technicians" just replace parts (often on a trial and error basis without proper diagnosis) and don't want to get their hands dirty.

Rant over.


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## Jezzie (May 24, 2020)

We've got a local guy who does all those sorts of repairs - but Weymouth is a fair distance from you&#8230;


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## StormENT (May 11, 2021)

MT-V6 said:


> Does your can gateway module show any faults? As far as I know the battery regulation and associated linbus is controlled via the gateway directly, unlike other modules which are connected to it via canbus


My only can gateway fault is DTC 01304 Radio Communication (Because there's an aftermarket radio installed).
I'm not 100% but I think battery reg is a virtual device via the can gateway, as you say, in the absence of a physical module on the negative battery terminal.
I think as I have the physical module then all errors are showing up via 61)Battery Regulation, whereas 19)Can Gateway shows nothing.


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## StormENT (May 11, 2021)

tttony said:


> Up till about 15 years ago we had a shop just a few miles away that just tested and repaired vehicular dynamos, alternators and starter motors. They had electric motors on jigs to spin up dynamos and alternators to test their output. Bearing replacement, brush replacement and even re-windings were their bread and butter. The guys wore filthy workshop coats and had carbon dust and grease on face and hands but provided a great service.
> 
> Nowadays nobody seems to have the skill or inclination to do that sort of work. Modern "technicians" just replace parts (often on a trial and error basis without proper diagnosis) and don't want to get their hands dirty.
> 
> Rant over.


I agree, and it's the reason I'm doing everything I can to avoid taking it somewhere.
My gut is telling me it's electrical, probably with whatever tells the alternator to activate thus the communication errors with the generator (If you can't tell the alternator to start then it won't), but I'm sure I'll be charged for a new battery, alternator, "Diagnostics" etc.... before they even start looking at the electrical systems.


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## StormENT (May 11, 2021)

SwissJetPilot said:


> Following on *Wolvez's* advice, have you checked the fuseable link on the battery terminal? Someone commented they were having electrical problems and only noticed one was broken under a very close inspection.
> 
> View attachment 4


Battery Terminal fuses look good









As do the Fuses to the right of the battery









In the *Ross Tech Forum* (linked below) that with the Valeo alternator it's possible to get the wrong regulator. Looking at the parts list both Bosch and Valeo seem to have a few different regulator revisions.

*J533 J367 and Generator problem Audi A4, B8, 2.0TDI Multitronic - 2008 Engine CAGA*
https://forums.ross-tech.com/index.php?threads/13952/

I seem to have the correct regulator. Here's the old one and the box of the new one I installed.
I'm going to investigate if there's a way to bench test the old voltage regulator and also try to work out for sure if the battery regulator unit is communicating with it at all.








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## StormENT (May 11, 2021)

A little bit further along my journey.......
Does anyone know the voltage the exciter wire should be to get the alternator going? With the car locked I get 12v+ (Battery voltage I think)
As soon as I unlock the car it drops to 9/9.5v and doesn't change from Ignition On, Engine Start/Idle and Rev'd.

I'm wondering if 9.5v is what the alternator want's or if that's the problem.

I'm tempted to feed it 12v from somewhere else and see if that fire the Alternator into life but I'm not sure if that could damage it?


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## Ed2312 (Dec 24, 2021)

Check the nut on the alternator. My car has done this and it was because the nut wasn't properly torqued. The plastic cover should be grey, if the connection is loose it will burn and cause it to brown. Remove it and check the nuts, if there is corrosion it is likely due to arcing from a bad connection.





How Do I Know If My Alternator Is Bad? 12 signs


The alternator and the car battery are tasked with providing electricity to your car for startup and for powering all the necessary car electronics. As such, both of these are vital components, and...




cararac.com


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## SwissJetPilot (Apr 27, 2014)

Also, check the ground connection located below the air box as it's a known point of contact corrosion. You can find it this area quite easily with the air box removed (note - this photo is from a 3.2 VR6). The bolts and cable terminals are somewhat hidden in this view but you'll see them as the location is common across the Mk2 line.


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## Knight-tts (Jan 29, 2019)

2 years ago I had a alternator problem One day the car just won’t start, Managed to get to a garage and the power cable had corroded , so new power cable installed at a cost of £76 plus labour


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## glavniq86 (23 d ago)

hello colleague, did you fix the problem and how? I have the same fаuld!


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