Hi Team,

So I have a Singapore market XKR that now lives in NZ. I've noticed that the dip beams are always on when I turn on the auto headlight function. The car seems to know when it's in the dark, for instance if the lights are in the off position and I pull into my dark garage the info screen says 'headlights off' as kind of a reminder that you're in the dark without lights.

I've done a scan with my autel ap200 and I can see my dedicated daylight running behaviour is set to 'North American Specification.

I'm aware that the small black sensor at the front of the dash is for the auto lights and isn't blocked. What I have noticed is someone before me has damaged the rain sensor under the rearview mirror - but as far as I know this doesn't have any effect on the auto lights, does it? Wondering where to go from here and if anyone might have encountered the same situation before.

 

From the workshop manual:

"The light sensor is incorporated in the rain/light sensor located on the inside of the
windshield, below the rear view mirror."

Therefore your rain sensor is the culprit. Is the entire sensor damaged or just the gel which attaches it to the windscreen? Does your rain sensor operate correctly even damaged? I'd assume not. Replace that part and both systems should work properly.

 

Thanks Cee Jay, I definitely agree that I need to sort out the rain sensor - it has a) broken at the plug and b) started to come off of the gel pad.

What is throwing me is in my workshop manual it seems to be the sensor in the dash that controls the lights:"The lighting system has an 'auto' lights function which is controlled by the CJB on receipt of signals from the light sensor. The exterior lights are turned on or off in response to ambient light signals from the light sensor via the instrument cluster."

Here's a shot of the book with the circuitry (pg 2263 in the 5.0 service manual). I do know that the sensor knows when it's dark as it will give me a 'lights off' message (which is triggered by headlamps not in auto/off and in a dark space). Hence wondering if it may be a setting I can change rather than a fault.

I'll replace the rain sensor any way and that may help me out - perhaps the docs are wrong or also uses the rain sensor.

 

Yes, I saw that also. The little bulb-thing on the dash is a light for the security system, and I don't see anything else there that seems relevant.
Does your mirror mount look like this from outside, disregarding all the bug guts?

 

I sure do, I've got that except mine has the silicone separating so more hazy. If the rain sensor is also indeed the light sensor then that'd explain it. I have a new silicone pad on the way so will try the simplest fix first (refixing to the glass) and move to replacement if that fails. The sensor plug is damaged but still allows a connection (terrible explanation and will post a pic in the thread when I get to it).

 

Small update here, I've fixed the rain sensor for now, but can confirm that that definitely doesn't do the light sensing for the auto headlights. I can do a test as follows in my dark garage:
1) Hold a flashlight over the sensor on the dash, with the headlights ON
2) Switch the headlights OFF, take away the flashlight
3) wait about 6 seconds
4) I see a message on the dash saying 'Lights off'

If I repeat that procedure without taking away the flashlight I never get the 'lights off' message, as the car senses that it's still in a well lit area. I did the same with the rain sensor itself and that made no difference.

So, that leaves a few possibilities: either the light sensor in the dash is practically dead and not functioning correctly (I doubt), something upstream (CJB/instrument cluster) isn't working, or there's perhaps some setting that can be changed to enable this (this feels most likely to me). Here's an excerpt of my light settings.

Some other notes - the auto lights turn on/off with the car, and I get the green icon on the dash telling me the headlights are on.





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Recently I've had a pedestrian warning light come up, which made me pull over and reset the codes. I noticed on the drive home that I had my lights in auto mode, during a bright summer's day, and the beams were in fact off! I stopped and covered the light sensor and the lights didn't turn on, but I did get a 'lights off!' message.

Ok, interesting...

I got home, turned off and on the car and the lights then became stuck in the on mode when set to auto, like before. Reading around this sounds like the switch itself on the stalk might be busted and not actually telling the car to turn on the automatic mode. Looking online it seems like replacements are relatively cheap, so might be worth swapping out and seeing what happens. Before doing that, I might see if I can diagnose this by removing the stalk and doing some electrical checks. Hopefully something in the wiring manual or the service manual might help with that.

 

If the sensor adhesive gets damaged, it can be removed with rubbing alcohol or similar and replaced with the appropriate width of silicone gel adhesive tape. I can't remember the width, but it restored sensor functionality after I had a clear ceramic film applied to my windshield.

 

Thanks to both of you. The manual is wrong in that although the car seems to use the black light sensor/alarm light on the dash, the rain sensor in the mirror is what actually triggers the auto lights. I had recently re-stuck the sensor with a new silicone pad and it now reacts properly to sunlight. I did try swapping out a light stalk with my father's F-Type but that did nothing - discovered it works while doing this.

Whoever replaced the windscreen (before my ownership) did a bit of a crap job and had half broken the sensor's connectors - my auto wipers don't seem to work but will test with a used unit shortly.