Can a bad headlight switch cause only 1 headlight to come on?
or should i focus my efforts on the headlight assembly?

car is an '03, factory lights, all other lights come on, the high beam comes on when you flick the lever, and the small bulb when you turn on the switch. Driving/fog lights also work fine
could the bulb be bad? or ballast?

I'm hoping something simple, but this a Porsche after all

Thanks
Brent

 

I've been tracing almost the exact issue for two months now with no success, try the following:

1- Check the light bulb
Maybe it's just that simple, swap both and see.

2- Check all fuses
even if they are not related to lights, I found some of them busted, others weren't but will effect the light in a way or another. Utilize current draw test to see if there is an electrical current flowing to lights or not.

3- Check the functions of the headlights
Disconnect the headlight unit from the car, with 12V small battery test the pins in the main connector and see if the light come on or not

4- Check ground points
I found some of them were loose, tightening them solved other issues but might work for you.

5- Replace ignition switch
It's significantly cheaper than the light switch, and known to cause weird electrical issues.

6- Clean / Replace light switch
Clean your switch with electronics connector, or you might just buy a new one.

These were the diagnoses steps I did so far, I organized them from easiest to hardest in my opinion. I had other plans to test the harness but sadly my engine gone few days ago.

Hope that helps you find the issue.

 

I was having issues blowing various bulbs in both headlight assemblies until I spent a few hours taping up a bunch of wires where the insulation was melted/deteriorated. Bulbs last a LOT longer now.

 

Thanks for the ideas

 

Yea harness up by the headlamps r known to detiorate. Pull the assembly and inspect.

 

Pulled the lights to inspect and changed out the bulbs while I was in there and all is good now, so likely bad bulb but I may have just jiggled the right wire also. We’ll see if it happens again soon, then I need to trace wires

 

When I changed my parking bulb, one of my headlights did not come on either. I just reinstalled and everything worked fine. I must have not had the connection "just right". Was very careful aligning when inserting the headlamp assembly.