My 06 XK8 has developed a weird headlight problem. After I turn on the
headlights they work for about 5 minutes and then the drivers side goes out.
If I switch to the high beams the same thing happens. If I turn the lights
off then back on they will work for another 5 minutes or so.

 

Specs vary - is it fitted with self leveling HID's?

Graham

 

If it happens on both dipped and main beam it sounds like a simple earth fault.
Main beam, dip and fog share a common earth point so see if your fog light stops working as well.
By 'Driver's' side I assume you mean LH?
If so the earth point is given as ENGINE COMPARTMENT, FORWARD OF LEFT HAND HOOD LATCH

 

Yes it has the self leveling headlights and it happens on both low and high beams. Also the fog light on the drivers side burned out about the same time this started happening.

I checked the grounds in the trunk and will look at the main headlight ground near the headlights.

 

I checked the ground in front of the LH hood latch and it is solid, the resistance from
it to chassis ground is less than an ohm. It sure does seem like a grounding problem though, especially with the LH fog lamp also out.

 

Both main beams and both dipped are fed from single relays so the problem has to be downstream of that otherwise the RH side wouldn't work..
The fact that it takes time for the fault to appear suggests it might be at the headlamp end rather than the actual ground tab, specially since you have confirmed it to be good.
Even so I'd check voltage between the earth tab and chassis ground when you have the fault. Your ohm meter is only putting a tiny current through it.
If that's OK then (I'm working from a 2004 electrical diagram but assume yours is similar).
The main headlamp connector should have the following sequence of wires
Pin 1 Red Sidelamp
Pin 2 Blue/Yellow Dip
Pin 3 Blue Main
Pin 4 Black Common dip/main ground
Pin 5 Green/white
Pin 6 Black

So if you can produce the fault and wangle some sort of probe into pin 4 (with it still plugged in) if you get 12V between it and chassis the earth cable is at fault. If you get 12V on pin 1 or 2 depending on which beam you're on it must be the connector.

 

Having same issue with same model.

 

Just to piggy back on this thread, I also have intermittent issues with the dipped low beams. Sometimes they work fine, other times they both dip and then rise on their own, usually after about 20 or 30 minutes running time. I guess they could be going off, dropping, then coming back on and rising again. Only happens on the low beams, and then, both at the same time. Interesting, as not all the time, and I cannot seem to find a common surround, like bumpy roads, curves, when approaching a car in front, etc. Just seems random at this point, except for the time before they sometimes fail.