Any advice? Audi have looked at it and said it's the 12v battery that's faulty, after another (indy) garage have said hybrid alternator. More inclined to believe the indy considering it's Audi's opportunity to squeeze out £550, compared to doing the warranty work! 

Surely the 12v battery should have been replaced after the first problem with the hybrid alternator anyway, as it's damaged it? 

Get the battery professionally tested Charlotte to prove the point. That means a deep discharge test drawing a huge current, not a simple multimeter reading of the voltage under little load.

When I had my alternator failure, the battery drained but this is a lead/acid type and can take a full discharge and recover. I think the dealer is swinging this so a professional test should prove it.

... but if the car is in the Audi dealer, they will insist the customer signs a cost waiver to pay for the battery test as described. I nearly did that, but once they'd put in writing that the BSG had tested good, I took it to an indy who checked it themselves, and, then replace the 12v for £370 (its 3rd battery since new)

 

 

Edited November 10, 2025Nov 10 by DieSel-Q

I'm in 2 minds whether to believe it's the 12v battery - it was replaced when we bought the car (broke down on way home from dealership!) in 2023, then wasn't changed when the alternator went, but have had a strange electrical problem with the door when sub-zero temps. Can't open door from outside (not frozen) but can open from inside but then car doesn't recognise door is shut. It only does this with the drivers door, it got checked at an auto electrician but they couldn't find anything, just that the voltage was on the low side (it was cold that day). 

Thing that's concerning is the indy that changed the brake servo sensor said it went to total failure when they tested it, and charged the battery so we could take it to Audi. At this point I wouldn't be surprised if it was both! 

If your battery is only 2 years old I cannot think it has failed unless one cell has gone down. Best get it professionally checked and show Audi the report.

1 hour ago, CharlotteW said:

I'm in 2 minds whether to believe it's the 12v battery -

Belief doesn't need to come into it if you get it tested.

Daft question - if I get the battery tested and it is faulty, what are the chances we can claim on the 3 year warranty? We just want the car driveable so we can get rid! 

I'm guessing fairly slim considering they'll just blame the BSG that's been replaced once? 

Your guess is a good as mine regarding a warranty claim, but if the battery has been fully discharged there is a possibility it has been damaged. Lead/acid batteries are more resilient than other types to discharge damage, but they are not completely immune.

Personally I would not take my car to Audi for a battery test. Audi has a vested interest in declaring it fine. Any decent auto electrician should be able do it. I believe even Halfords will do it, though they would not be my first choice. Ensure you get a printed test report from whoever you choose.

Amazingly after asking for a second opinion at Audi, they have decided there is nothing wrong with the car, and we just need to monitor it 🙄 

Be taking it straight back to the indy garage to have a proper look, test the battery and get a report! 

30 minutes ago, CharlotteW said:

Amazingly after asking for a second opinion at Audi, they have decided there is nothing wrong with the car,

Told you so. It is now standard practice for Audi to deny all responsibility and deny all warranty claims for all defects.

What was once a prestigious car brand is now a maker of shoddy unreliable junk. O how the mighty are fallen!

Hi everyone,

I’m building evidence to support a case with The Motor Ombudsman regarding the failure of the Belt Starter Generator (BSG) on 48 V mild-hybrid Audi models.

My own vehicle is a 2022 A3 35 TFSI MHEV, which suffered a BSG failure at 47 k miles. Audi UK refused goodwill, claiming the ignition had been “left on,” despite no diagnostic proof. Since then I’ve seen many similar reports across A4, A5, A6, A7, A8, Q5, Q7 and Q8 models. ( no A3 so far)

I’m now trying to compile concrete examples of cases where Audi provided goodwill or extended warranty coverage for this fault, they have closed the case and refuse to engage as the technical bulletin does not cover A3's despite being the same part.

If you’ve had your BSG or 48 V system repaired under goodwill or warranty (even partial), could you please share:

• Your model & year

• Mileage at failure

• Dealer name & outcome (goodwill %, warranty, or full cover)

Any screenshots, invoices, or redacted correspondence would be hugely appreciated (DMs welcome if you prefer privacy).

My aim is to present verified evidence to the Ombudsman to show that Audi has already accepted this defect in other cases and should apply consistent treatment. This has been such a horrendous experience, I honestly love Audi cars but I can't believe the way they have treated me. They are just ignoring me at the moment.

 

— Clare Williams
2022 A3 Sportback 35 TFSI MHEV | Case 00302983 (Motor Ombudsman)

Hi Clare 

• Your model & year  - Audi A6 C8 Avant 50Tdi Quattro 2020 model MFR’D OCT 19

• Mileage at failure  - I think about 78,000 at the time. (I was not given paperwork)

• Dealer name & outcome (goodwill %, warranty, or full cover) - Excellent Customer Service at Caffyns Audi Eastbourne - BSG Changed 100% Free of Charge.

• I referred the dealer to the following website:       https://www.check-vehicle-recalls.service.gov.uk/recall-type/vehicle/make
   

• It is important to appreciate that some ‘recalls’ only apply if a fault is reported, rather than the proactive contacting of owners.

• screen shot below.

• have a check for you vehicle.

Hi Alex,

 

I am so grateful, thanks! Yes my VIN does not have a recall and this has been refused but i am going to try and fight it. It's the same issue and part!!

My audi A6 2019 50 TDI Mild Hybrid quattro C8 had an issue with its alternator. Milage is about 79000. I've had a mechanic provide me with the fault codes from their diagnostic checks. Please see below.

U046900
U350100
U140A00
P056100
P056200
U140000
U101100
C11CB01
U140B00
B1297F5
P175000
P0A9400
C113AF1
P0B2900
P1B1600
P0562
U3501

I have a diagnostics check booked with Audi on 7th January 2026 for £150. When does the 7 year warranty expire? I'm calling them daily to try and get an earlier date. But I think they've caught on and don't want to give me an earlier date. I've had the battery replaced via Halfords because I thought that was the problem. My issue happened in mid November 2025. Some audi agents who have checked my car REG, VIN have said that according to their own database there is no recall for my car's alternator or maybe the car. I don't know if they are just trying to put me off going to them. 

A lot of Audi agents have told me that they can't confirm that my car's alternator is covered under the 7 warranty until I do a diagnostics check with them to pinpoint the problem. I assume that if it is then they have to refund me the £150.

I'm aware of this https://www.check-vehicle-recalls.service.gov.uk/recall-type/vehicle/make/AUDI/model/A6/year/2019/recalls

The cheapest quote I've got from a mechanic is £2200. I don't even wanna know what Audi will try and charge.

Can someone please help me fight this?

Edited December 3, 2025Dec 3 by Forbzy

7 years starts from the car registration 

 

I didn't buy the car from Audi. I've owned it for just over 4 years. The previous owner or private dealer might have registered it with audi. Is there anyway of find out? When you say registered do you mean the day/month/year the car was manufactured?

 

Thank you for getting back to me so quickly. Audi and this car have given me so much stress.

Edited December 3, 2025Dec 3 by Forbzy

25 minutes ago, Forbzy said:

Can someone please help me fight this?

Have you read the entire thread? There is a lot of useful information within.

31 minutes ago, Forbzy said:

I didn't buy the car from Audi. I've owned it for just over 4 years. The previous owner or private dealer might have registered it with audi. Is there anyway of find out? When you say registered do you mean the day/month/year the car was manufactured?

 

Thank you for getting back to me so quickly. Audi and this car have given me so much stress.

7-years warranty begins from the moment of FIRST registration of the vihecle. Number of previous owners does not matter.  

Edited December 3, 2025Dec 3 by Roman_DE

Thank you. My car was registered in June 2019. The 7 year warranty should expire June 2026.

Did any of you have to escalate to senior management to get Audi to cooperate? If yes do you have any email addresses for escalation?
Did you present any evidence of other owners (especially in the UK) who had a faulty alternator and Audi resolved it free of charge?
Did you have to get legal aid?

20 minutes ago, Forbzy said:

Thank you. My car was registered in June 2019. The 7 year warranty should expire June 2026.

Did any of you have to escalate to senior management to get Audi to cooperate? If yes do you have any email addresses for escalation?
Did you present any evidence of other owners (especially in the UK) who had a faulty alternator and Audi resolved it free of charge?
Did you have to get legal aid?

When I got this trouble with alternator (A6 C8 3.0 diesel, 80Tkm) I reported to Audi dealer. Brought the vehicle to the dealer and they told me themself that the alternator was under 7-years warranty. Thus, replacement absolutely free of charge. No escalation, nothig was required. Main point is that: there should be failures in the control module of alternator. Germany. 

If I were you, I would clear the matter with Audi headquarter in the UK. They must confirm you the alternator is under extended warranty. 

Edited December 4, 2025Dec 4 by Roman_DE

1 hour ago, Forbzy said:

Thank you. My car was registered in June 2019. The 7 year warranty should expire June 2026.

Did any of you have to escalate to senior management to get Audi to cooperate? If yes do you have any email addresses for escalation?
Did you present any evidence of other owners (especially in the UK) who had a faulty alternator and Audi resolved it free of charge?
Did you have to get legal aid?

Thankfully, we knew someone that worked there that could send us the recall bulletin from Audi - I left a copy of it in the car and took a copy to the service desk armed and ready. Was also told that I'd have to pay diagnostics if that wasn't the problem, but came back pretty quickly it was the alternator. Audi also paid for a like for like hire car as they had nothing available - funnily enough when they realised how much it was costing the the car was fixed about a week quicker than they estimated (I was under 25 and costing them about £300 a day in insurance from enterprise for the E-class we were given!). This was Audi Sheffield, for reference. Thankfully, we've just collected our new car and PX'd the Audi! 

The agent on the phone always tell me my car isn't a part of a recall campaign. Can't seem to get an earlier appointment for diagnostic checks.
@Roman_DE OK I'll email Audi UK headquarters.
@CharlotteW Do you still have a copy that recall bulletin?

There was no recall. Audi just waited till the alternator failed thn took responsibility.

Should've been a recall in my opinion!