Battery or alternator issue

[Bealsy]

Afternoon All,

Hopefully some knowledgeable, kind folk on here can help with an issue I have before I start going down various rabbit holes.

Recently been have two intermittent error codes pop up on my T6.1 2021 plate. Whilst at the VW specialist garage yesterday for MOT, Oil and DSG service asked them their opinion.
They came to the conclusion of faulty alternator, however this was replaced by previous owner with a reconditioned Bosch in April this year.

The faults I get are Manoeuvre braking unavailable and Parking distance control.

Got my meter out this morning and measured the battery at the following intervals:

12.1v with ignition off
12.0v idling
11.7v idling under load - Lights on, electric seats on and Fan on to 6
13.6v once engine is revved slightly and then sticks at 13.6v rising to 13.8v while still idling.

Did some research (Chat GPT) and this threw up suggestions of battery not coded, incorrectly coded or BMS is confused or faulty rather than alternator at fault.

Anyone had similar issues and fixes?

 

[Dellmassive]

try it with the fan on blower #2,#3

try it with the headlights on.

you got stop/start?

smart alternator?

sensor on the battery NEG post?


post some pics of the starter battery.

how old is the battery?

 

[Bealsy]

Thanks Dellmassive

yep did the above under load 11.7v

Not sure I’m understanding your smart alternator? What’s to check here?

Since I reconnected a wire to the positive terminal as suggested on here the Start/stop is working. It’s not our daily driver, only had the 5months and can go a week or two without moving.

What is the sensor on battery neg post I need to check?

 

[Bealsy]

Thanks Dellmassive

yep did the above under load 11.7v

Not sure I’m understanding your smart alternator? What’s to check here?

Since I reconnected a wire to the positive terminal as suggested on here the Start/stop is working. It’s not our daily driver, only had the 5months and can go a week or two without moving.

What is the sensor on battery neg post I need to check?

 

[Dellmassive]

this is the sensor on a T6.1

 

[Bealsy]

this is the sensor on a T6.1

View attachment 310348

Can it be checked with a meter if so how?

 

[manfrotto]

What were the fault codes you had?

I vaguely recall seeing somewhere that the voltages you are getting is due to the smart alternator and is normal, but stand to be corrected.

 

[DXX]

@Dellmassive asked you in post #2 how old the battery is?
2021 van, battery is degraded if it is the original and especially if only driven once every 2 weeks.