[Gmart92A]

Thanks - great idea on swapping bulbs - I'll give it a try.
After thoroughly looking over the housing, it does have venting but I would not consider it active while driving (not allowing airflow through that could help dry it faster.
Thanks again - I'll report back after bulb swap.

 

[Gmart92A]

Thanks for finding and posting this document! I believe I fall into the "replace lighting component" category which is financially devastating... maybe a little dramatic, but a replacement assembly is $$$.
I have cleaned the vent and the filter paper could probably stand to be replaced, so I may fabricate my own.
Only practical thing I have seen on YouTube is to silicone seal the entire perimeter. I am going to do an air test and see where the leak(s) are coming from first.
Thanks again for helping!!

 

[Gmart92A]

Just an update - I have swapped bulbs from PS to DS and vice versa, and the failure stayed with the PS or right side assembly. I think the best next step is to replace the ballast. These things, based on this D3S spec light are hard to find unless you pay full dealer price, but I did find a couple possible vendors.
The main issue, however, is keeping moisture out of the housing (which I think is what took out the ballast). I pressure tested the housing with all possible vent areas sealed and there does not appear to be any leaks around the perimeter. With the bottom vent tapped over, the air finds a way out at the main harness connection, so wondering if that area is the culprit... To be fair, we have had the wettest, humidest summer ever up here in south-central Wisconsin, so thats something. With the housing all dried out now and reassembled to the vehicle, moisture will probably show up again soon. I'm kinda stumped on the moisture problem... ultimately, may have to break-down and buy a whole new light assembly... ugh.

 

[Gmart92A]

Update - found ballast well below dealer cost and it corrected the issue with the low beam HID Xenon light. However, still can't track down why moisture enters the assembly... stumped. I put a couple of desiccant bags in there, but not confident in these handling the moisture problem. Cheers to @Iradkov for helping me diagnose the light issue.

 

[Gmart92A]

Do you have a link for the replacement part?

Thanks.

Porsche Cayenne (2015-2017), Xenon Control Unit, Hella, 95863159701 (betaautoparts.com)
Thanks for reaching out and sharing your story. I will try harder to locate my leak and seal that baby up!
The link above is for the ballast. I was not willing to pay Porsche replacement price and searched like hell to find an affordable replacement. When I first noticed this supplier was in Saudi Arabia, I was skeptical. However, I was pleasantly surprised with their professionalism and response. They even emailed to verify my model to ensure proper fit. I was provided DHL tracknig number and received the part in 3-4 days after ordering. I installed it today and it fixed the issue. Let me know if you have any more questions. I think I paid $144 total with Int'l shipping.