Battery draining?

[Rabbit]

Hi Guys

I have a 20 plate Golf GTI.
My car has been running fine until last week. I started the car, and it completely struggled as if the battery was drained, then quickly died. I called RAC who tried to jump start it, which didn't work. He then disconnected the negative on the battery for 5 minutes, after that the car started up. He said it was more than likely a "module malfunction", I then had 27 erros on the car which all cleared when I drove off.
Fast forward a week and the same thing happened again, this time i jumped the car and it started. Earlier today I started it again and it's as if the battery is draining because the display and lights seemed dull when turning the car over. Halfords have checked the battery health and alternator which are both OK.
VW want £180 for a diagnostic
Has anyone come across this?

Thanks in advance

[Beebopper]

Sounds like it's going flat when it's parked, not running? So perhaps can rule out an alternator issue, but have you tested the battery voltage and how old is the battery? Could need a new one.

Also, have you done anything to the car, fitted anything electronic (e.g. dashcam) since this started happening?

If nothing has changed and it's started randomly, test the battery and get it on a decent re conditioner / charger like a CTEK MXS 5.0, if the battery is 5-years old (from new), you could take a punt and change the battery for a new one.

Oh, and presumably you have checked the interior light are off yes? (Have to ask but assume you have!).

[Exonian]

The boot light may be worth checking as they can stay on and be completely unseen when the car is parked up.

Going back around 18 or so years I had one of the first Polo GTI 1.8t’s and that car had an issue with the factory nav headunit draining the battery when the car was switched off, locked and parked. It had to go back to VW for an update of some sort.
Admittedly the mk8 Golf is a very different generation but that said, there’s even more electrical things quietly running in the background even when the car is switched off. Usually these power down after a short time but if there’s a fault then it might take a dealer to find it.

Hopefully it’s just a battery on its way out though.

[valentino]

Probably a silly question, but is your car left in a secure garage, but you leave the car unlocked?
I had been doing that for years with previous Golfs. Then i got a MK8, left it unlocked in the garage for a couple of days, and the battery was flat
called VW assist, managed to get it started, but had loads of faults showing, but they went after a while. He said that the car never actually sleeps if you leave it unlocked.
Now it gets locked, and on a trickle charge if im not using it for a few days, and its fine

[fredgroves]

If you've never changed the battery and it still has the original, probably change it.

They last about 5 years normally...

[joe6]

If you've never changed the battery and it still has the original, probably change it.

They last about 5 years normally...

My 2019 gets a regular battery top up trickle charge and is still fine. I have a dash cam with parking setting so there is a battery drain from that when parked up. Does the stop/start work? An indication of low battery voltage. If fitting a new battery remember to code it to the car.