Author Topic: Reasons for temperamental HID headlight  (Read 627 times)

Offline Chew22

  • GTI forum regular
  • ***
  • Posts: 134
Reasons for temperamental HID headlight
« on: 12 May 2021, 22:06 »
Hi everyone, back after about 9 years!!

I've recently picked up  a 2014 MK7 Golf GTI PP which comes with HID lights.

I keep getting a warning on the dash telling me to check my dipped left headlight.

It seems that there is an intermittent fault as sometimes the light works great and sometimes it doesn’t. When I sit in my driveway and turn the headlights on and off the right one always works and the left works some of the time.

I paid VW £60 to diagnose and they just went off the fault codes and told me it needs a new bulb, to which they quoted me £440 to change!

The exact notes they wrote were ‘Customer complaining that the vehicle is showing warning message left dipped headlight. Sometimes works, sometimes does not. Carried out general fault finding, relevant faults logged B121700, B121715 L13 NS dip beam bulb open circus. Requires bumper removal to replace bulb.’

Does this sound more like a ballast issue and highly unlikely to be the bulb?

I don’t think it's a loose connection as the car will be sitting still and turning the lights off and on gives mixed results.

As VW have said it’s a bulb and not the ballast, the warranty company wont pay for the repair.

Would the most sensible thing to do at the moment be to personally swap the bulb with the other headlight?

Any advice would be great, thank you!

Offline Agreeable Slick

  • Global Moderator
  • Serious forum addict
  • *****
  • Posts: 7,116
  • Unit
Re: Reasons for temperamental HID headlight
« Reply #1 on: 13 May 2021, 09:19 »
Unfortunately getting to some of the bulbs on these is a right pita. There are DIY guides which you can find where they remove a load of stuff from inside the engine bay to get at the back of the unit, but it's more effort than it's worth to do that, so it's just easier to pull the front bumper off and open up your access to the light unit.

DAP have loads of great videos for MK7 related issues, here is the one to remove the front bumper and pull the light unit out;

It looks daunting but it's dead easy and once you've done it you'll be able to get it on and off in the future dead easy.

I made this : ->

Offline Chew22

  • GTI forum regular
  • ***
  • Posts: 134
Re: Reasons for temperamental HID headlight
« Reply #2 on: 15 May 2021, 12:55 »
Just to update.

I swapped the bulbs round and it turns out it was a faulty bulb. I have replaced both of them and all is now well.

It's def worth doing this supposed to assuming it's the ballast as the symptoms are pretty much the same.