I've recently bought a Cayenne Turbo and after a month or so the LH headlamp started to develop condensation inside the lens housing.
I took the headlamp unit out and dried it out (gently!) with a hairdryer and it worked fine.
After a couple of (very wet..!) weeks the problem came back. Same routine, I took the unit out and dried it with a hairdryer. Now the dipped/hi bi-xenon light, the cornering light and the additional hi beam have stopped working.
The sidelight and indicator are still working. It looks like (from the Owners Manual) there are 2 fuses indicating seperate 2 circuits. Both appear to be intact and not blown.
Before I spend some cash taking it to the dealers does anyone have any suggestions...???

 

Either a crack in the housing or it's not sealing. My guess is crack.

 

Condensation is actually a common problem for Cayenne headlights, especially in humid climates. Porsche issued a TSB to correct this problem with the insertion of a desiccant material to absorb the moisture inside the headlight. My guess is that the reinstallation of the headlight brought up another issue, which also required a TSB - the headlight connection issue. Both items are a relatively easy fix.

 

Now that your cornering lights stopped working, you have a bigger issue than finding out how the moisture got in there. If you have a Durametric, then I suggest you hook it up and look for error messages under the headlight modules. Record the errors, then try to clear them out. Then take it from there...