I noticed my headlights flickering last night on my 2006 Boxster. I just got the car a couple months ago and haven’t driven it at night much so I’m not sure if this is a new problem or preexisting problem.

Today I looked closely and it is not only both headlights but all lights. Posting a video of the flickering wheel well lights below. The HVAC was off during this video.

It only flickers when the engine is running and doesn’t seem to be speed dependent. It flickers at idle or when I’m revving.

I connected an NT530 and read the DME supply voltage off it while running. It fluctuated between 12.4-13.7V. I’m unsure what is normal so this is just info. Also including a video.

Where would Rennlist suggest I start looking to diagnose?

 

Voltage fluctuation video here

 

Try and put an analog meter on your battery, as not sure the sample rate of a slaved OBD read out is too helpful.
Regardless, alternator and charge control circuits do fail and switching transients is one manifestation... noting of course, alternator output varies continually depending on load, and you may have a perfectly functional charge circuit, but a fault load device switching in and out (similar to turning a load on and off regularly).

 

As Kuro said measure on the battery if you can. Normal resting is about 12.6, running the engine it will typically rise to approx. 13.5 to 14.5 volts.

"One of the most common causes of headlight flickering is a dying battery."

 

If you don't already own one, I would highly recommend purchasing a battery maintainer; a lot of folks on these forums plug them into their cars when not being driven. I would routinely plug mine into my Cayman if I knew I wouldn't be driving it in the next 2-3 days; same goes for my Cayenne now. They maintain the battery as if the car were being driven, and can be left plugged into the car for as long as needed. (Unlike a trickle charger, which can ruin the battery if left plugged in long enough) CTEK is a popular brand with people, and may actually manufacture the units Porsche brands and sells. They're relatively cheap when compared to all the other parts that seem to be faulty, and may just repair your battery and fix the problem.

 

I measured voltage at the battery with a multimeter

-Voltage with car off is 12.3V
-14.2v when first starting. Fluctuates plus or minus 0.01V, so negligible
-14.0V when idle slows down a bit. Same fluctuation
-13.5V when warmed up at idle. Plus or minus 0.02V.
-13.6V with my wife reviving the engine around 2-3k.

I took it to O’Reilly and they said the battery, alternator, and diodes are all good.

Oddly I couldn’t see any flickering today but it was midday. Could just be hard to see. I’ll check to see if I can see anything tonight.

So either a) alternator and battery are good or b) it’s an intermittent issue.

If a) I’m assuming it’s a wonky switching load or a bad ground somewhere. HVAC and radio were off which leaves coils and …, well I can only think of coils as a switching load after those. Lights would be constant.

If it’s b) then FML. Nothing worse than figuring out an intermittent issue.

 

Reading your post again. You said analog meter. Would analog be preferred to a digital multimeter?