I have searched and realize auto-headlights malfunctioning has been discussed but I can't find any discussions with issues like mine. 2005 XK8 - sometimes when in auto mode the headlights work as intended, but sometimes the headlights won't come on unless in manual mode. When they don't come on as they should in auto mode the dash lights do (but not the headlight indicator light), so I would think that would eliminate a sensor problem. When they do come on initially they will spontaneously go out while driving but the dash lights remain on. Any ideas?

 

Same 2005 MY so we both have HID's with auto headlamps. Risky to assume your US spec and my UK spec are designed to work identically but they should be pretty close.

My instrument pack lights are on all the time even though it can be difficult to tell in daylight. I only really appreciated that when all four blew recently and I was left with no main instrument illumination. With no headlights on, the rotary dimmer doesn't do anything.

In auto mode, the headlights tend to come on a little earlier than I would be switching manual ones on but better too soon than too late. When the lights are on, the sidelight icon illuminates in the instrument pack and the rotary dimmer is available.

If the wipers are switched on in auto for more than 20 seconds continuously, the auto headlights switch on regardless of external light level.

With the auto headlight facility turned off, 'Lights are off' warning appears in the instrument message panel if exterior light level is low enough for the external lighting to be on if it were set to auto.

If you feel at times it's sufficiently dark for the auto lights to have come on and they don't, I'd have thought sensor.

Graham