I always leave my headlights set to AUTO, this morning I walked out to find my headlights on and drivers side window down about 1/2". Lights were off and windows up the last time I saw the car, about 10:30p. So sometime during the night, the car turned on the lights, HOW?

I did replace the battery Saturday, so I am hoping maybe it was not fully charged.
BTW: been raining 6 days straight here, so I am wondering if that is an issue also, as I have the defroster on, headlights, wipers and rear window defroster on, nearly all the time.

 

I also leave the headlights permanently set to AUTO on both current 2005 and previous 2001.

The window drop is a classic symptom of low battery but the headlights shouldn't ever stay on with the ignition key removed ...............?

(it's snowing right now so I'll leave it to someone in sunnier parts to prove / disprove that theory!)

Graham

 

Slightly related subject, I have noticed over the last few days that my auto headlights are going on even in daylight applications and not just evenings or under overpasses etc. They are going on and staying on much longer than I would expect. Can the sensor possibly be dirty, and where is it?

 

Are you sure it was the auto headlights that were on as opposed to the dip beams that could have been switched on with an inadvertent press of the headlight button on the key fob before you reached the car?

Window drop is more difficult to explain! Need to give that a bit more thought!!

 

I parked my car at 8p, last time I saw it, at 10:30p lights were off and then at 9a, the lights were on.

 

It seems to me that your problem might be an ignition problem where the accessory setting might not be switching off all the way when removing the key and then triggered the lights going on. I have had cars in the past where when pulling the key did not stop things like the radio from staying on. Worn out ignition cylinder could be one possible explanation.

 

Hi.

When removing the key, there is a small flap moving to cover the ignition key hole. If this flap gets stuck in the "open" position, which is a common fault, the electrics won't turn all the way off. Neither will you be able to lock your car if this happen. The flap can be carefully cleaned and lubricated with some graphite to fix it. At my age you need reading glasses and a flashlight to check.

 

Did it start OK?
If so the lights couldn't have been on for long.
I don't know enough to say if the key flap Oyster describes would let the lights come on - it does stop the car 'going to sleep' but if it was the ignition not switching off your lights would have been on when you left the car in the evening.
Taking the key out turns off headlights but not parking lights (in a UK car anyway) for obvious reasons.
This is a most curious happening unless Astromorg is right and you had a thumb problem.

 

Hi again.

After having studied the electrical diagram, I don't think the flap I mentioned has anything to do with the headlights. But you never know with these cars electronic wonders. It was actually a "shot in the dark", which is probably not the right expression since the lights stayed on.

 

I think it's still worth putting a dab of graphite powder in the ignition cylinder lock. That could turn out to be the magic fix. And while you're at it, lube your drivers door lock as well....

 

tberg, the sunlight sensor is the one on the dash. The rain-sensing unit is in the mirror (or the arm to the mount). Clean the one on the dash and see if it perhaps has a film or dust affecting its ability.

 

H20boy and tberg
Are you sure about the sensor on the dash? I thought that one told the air conditioner how hard it had to work. I ask this, because I had the same problem as tberg. I also noticed that my rear view mirror was vibrating more than normal, and found that it had slid down a little bit. It was not firm in its holder.

Anyway, I pushed the mirror back up into its proper position and it stopped vibrating and my headlights quit coming on during the day. My theory was that the headlight sensor had dropped far enough to be behind some of the blackened area on the windshield

Like I said, it's only a theory, but it worked for me. Might want to give it a try.

Good luck,

Darrell

 

The Solar Sensor (dome on the top of the dash) is an A/C system sensor:



It's one of 5 sensors that feedback information to the Air Conditioning Control Module (A/CCM) which automatically adjusts air temperature, airflow volume and distribution from the air conditioning unit to maintain a stable passenger compartment average temperature under changing weather conditions.

The others are:

External ambient temperature sensor
Motorized in-car aspirator
Heater matrix temperature sensor
Evaporator temperature sensor

Graham

 

The auto headlight sensor is in the bulbous housing under the rear view mirror along with the auto wiper sensor. Also in that housing is a small circuit module for the sensor. This sensor is connected to the body processor module.

 

My lights are also stuck on in Auto mode, I belive that there is a fault with the light sensor or the conditioning circuit in the mirror pcb as I tested on the bench and there was no change in the output signal regardless of light or dark conditions. I will live with the problem as a new mirror costs more than a weekend ski trip!

This is the rain sensor.



This is the lightt sensor.



And the mirror pcb.

 

I just had my windscreen replaced ... auto headlight sensor might be affected as the lights stay on when switch placed in "auto", but sometimes will go off after sensor exposed to sunlight for at least 5 min or so, like it's supposed to, but sometimes headlights won't go off unless car is turned off, sits a while in daylight, & then restarted.. "Dark" area behind rearview mirror is likely the culprit as it may be larger than the original thus shading the sensor a bit.

 

Hiya Jon,

Just had to say thanks for mentioning shooting some lubricant into the ignition and door locks - might add trunk to that list.

Awhile back, my key didn't seem to 'work' -- I was happy my sister had the logical thought of 'hey, see if this works'. Magic.

All of a sudden, I was like - hey, these are smooth and easy now! Hello?!

Simple things to keep in mind.

Thank you!

Sandy

 

O.K. I'm confused .... is the light sensor in or part of the the circuit board of the rear view mirror ... or is it in the mounting stalk assembly that is adjacent to the windscreen where the rain sensor is located ("glued" in place) ????

 

For a 2003 car the sensor is mounted on the screen with signal conditioning done by the PCB in the mirror.

 

Well, I hope you are correct as I'm going to purchase via Ebay a decent looking used rear view mirror assembly. A new one, on line price, is close to $500., and used ones are about 1/3 that price. I have one supplier swears that the black dome on top of the left hand side of the dash senses light for the auto headlights on/off feature. Mine are now staying on constantly ....even in bright daylight. They used to turn on only at dusk or going under a long overpass.
At the moment, I'm convinced the black dome on the left side of my dash on my '05 XK8 is sensing how hard the a/c unit has to work & has nothing to do with the lights on/off feature.