Weird headlight electrical issue

[derekmines]

I'm clutching at straws here wondering if anyone has experienced this issue before, or knows the Cayenne electrical system well enough to attempt a diagnosis.

Here's the details (my truck's a LHD 2005 Turbo with Xenons, cornering lights etc)

If both headlights are connected then when the lights come on, the passenger side works perfectly, the drivers side dipped light illuminates, attempts to self level and then goes out, generating a warning symbol on the dash. The sidelight stays on, indicators work fine etc

If i then tap that headlight the dipped beam unit will come back on and stay on for as long as the car is running.

If I disconnect the passenger side light completely then the driver's side works perfectly every time.

The moment I reconnect the passenger side, the drivers side starts playing up again.

What on earth could be the cause of this?

[Loren]

Sounds like a bad ground to me.

[martadon]

Just recently, I had a screwy problem with the right front turn signal and right hi-beam operation. turned out to be the short wiring harness from main harness to headlight assembly mounting tray. insulation was cracked and falling of. No shorts and all volt-ohmmeter readings worked. changed harness, voila! Fixed.

[derekmines]

Similar to mine I think... I finally got bored last weekend and took the front of the car apart with the intent of fixing the issue... after swapping various parts around to try and replicate the fault I ended up figuring out that it was the headlight carrier on the offside.

This headlight carrier has two clips to hold in place the short harness you mentioned, one of those clips was broken.

With nothing to lose I took a dremel to the carrier and modified it so that the harness now plugs straight in the back of the headlight.... 500km later and not a headlight warning in sight. (as an aside, the dipped lights no longer flicker either!)