Help with Bi-Xenon dipped beam fault please - 2002 996 Turbo Coupe Tip

I'm hoping for some advice from the wise and gracious members of the forum on the next stage of troubleshooting for an issue with the Driver's Side Bi Xenon (HID) Dipped Beam on my 996 Turbo (2002 Tiptronic)! I've owned the car for just over five years, and until recently both lighting systems had been completely reliable. Original symptoms​ Two faults appeared at around the same time: The left indicator light on the dash started flashing rapidly . The front left (nearside) indicator wasn't illuminating at all when switched on (turn signal and hazards). Whilst investigating the above, I noticed that the driver's side (right-hand) dipped beam (Bi-Xenon) had also stopped working. Given the age of the car (now over 20 years old) and the fact that I hadn't replaced any of these bulbs during my ownership, I assumed I simply had a couple of failed bulbs. I don't know whether the faults occurred both at the same time, or independent of each other and I only noticed when the rapidly flashing indicator signal light informed me that there was an issue with the indicator circuit (I haven't driven the car in the dark for quite some time now). What I've done so far​ Checked fuses. Replaced both dipped beam Xenon bulbs . Replaced the front left indicator bulb . Neither repair fixed the respective fault. For the indicator, I then replaced the indicator bulb holder with a brand new one, which forms part of the electrical connection. That immediately solved the indicator issue, so that fault is now resolved. For the dipped beam, I swapped the ballasts from left to right. The fault stayed on the driver's side , which seems to rule out both the bulb and the ballast. Where I am now​ The only remaining fault is the driver's side dipped beam . I'm only a DIY mechanic, and I know the Xenon bulb connections are a bit fiddly. There's a small possibility I haven't seated or connected the bulb correctly on that side, although I completed the same job on the passenger side without any issues and that light works perfectly. Assuming the bulb connection isn't simply my mistake, what would you investigate next? My thinking is: The passenger-side dipped beam works normally. Swapping the ballast made no difference. A new bulb made no difference. That makes me wonder whether I'm looking at a wiring issue somewhere after the feed splits to each headlight (as the passenger side dipped beam has worked perfectly throughout), or perhaps something else that's common on the 996. Would the next logical step be to get hold of a wiring diagram and start tracing the driver's side dipped beam circuit with a multimeter? Are there any known failure points, connectors, earths, relays or control modules on the 996 Turbo that I should check before I start pulling the loom apart? Any advice from those who've had to diagnose this before would be much appreciated!

Oh dear God, if ever there was a case for not googling possible causes of car faults, this is it. Some absolute horror shows of headlight wiring out there...

The headlights are known to not seat correctly occasionally, you could try pushing it into position a bit harder, also take it out again and inspect the connector and socket as the mounting can break!

Thanks, I'll take a look, but the rest of the lights on that side work fine (indicators, main beam and side light) and I've already taken it out and put it back in at least three times (once for bulb, once for a different ballast, once for swapping the ballasts over). I've been trying to find how to access the wiring loom behind the light (from the connector) backwards, but can't seem to find anything. Can you access it by pulling the frunk lining?

You can see the back of the connector and ballasts when you remove the front section of the arch liner, but its not very accessible. The loom heads of towards the frunk. A quick search found this thread from Rennlist which has a row (rest of world) headlight wiring diagram https://rennlist.com/forums/996-turbo-forum/1025627-2002-996-turbo-wiring-diagram-headlight.html

Thanks Mac, I think this may be a bit beyond me - perhaps its time to get an auto electrician in...

if you remove the frunk plastic cover you can access the headlight controller.

Oh no, not another computer?! Sounds expensive! Probably makes more sense that it could be the headlight control unit that's on the duff though - the wiring in the back of both headlights looks in ok condition and I suspect they would be the worst out of the bunch as they would have had more extreme heat cycling then the wiring tucked away in the wing? Looks like you can pick up the headlight control units pretty cheaply (they're £600+ from Design911!) so that might be worth a shot, fingers crossed they don't need coding... https://www.ebay.co.uk/itm/147472733354?mkcid=1&mkrid=710-53481-19255-0&siteid=0&campid=&customid=&toolid=10001&mkevt=1

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sorry is this mess your car or a pic from the Internet? If it's your car it's time to leave it to the professionals to sort out whatever a PO did

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No, that's a pic from the internet - it seems the Americans have had some serious issues with the headlight wiring on 996 era Porsches degrading. The wiring on mine that I've seen looks fine.

Managed to pull up some photos, mind you mine's not a turbo but fairly confident it's the same-ish, the headlight controller is the black box to the left of the CD changer, to investigate the yellow connector itself as you can see you might as well do it from the front with the headlight removed, removing the liner doesn't give you access to much to investigate

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Thanks for the pics - very helpful!

OK, so I swapped out the head light control unit for a used one (same part number) and no change in symptoms - parking light (small bulb) comes on, but no dipped beam. Looking around the headlight control unit, all of the wiring seems fine, so no idea what the issue is. Does anyone have any pointers please for things that I could check before waiting 3 weeks to get it booked in and then taking it into the garage and no doubt handing over £200+ to get it fixed?

I'll have a look at the wiring diagram after and come up with a couple of checks to do with a multimeter. Something to try for now is to swap over fuses A9 and A10 and see if anything changes!

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what about where the loom goes into the firewall? accessible to by removing the cowl to the left of the battery tray? If that all looks fine I'd be suspecting the yellow plug where the light clips in. Have you taken a look at the pins themselves? Maybe one is bent or broken