The rearview mirror was bad when I bought my 99 XK8. I replaced it with an auto dimming aftermarket mirror. It works just fine, but now my auto light function does not work. I understood that when I made the change. It was more important to have a working rear view mirror than to have the auto headlight feature working. I saved the old mirror and may one day try to incorporate the sensor back into the circuit. The best solution is to replace the mirror with an OEM one if you can find one and can afford it.

 

I was able to transplant the auto-light sensor circuit into an aftermarket mirror with a monitor similar to what is described earlier in this thread. YMMV depending on the space in the housing. It likely will require some component relocation on the circuit board, and some very careful printed circuit board edge grinding. Doable if you have decent soldering skills.

 

Would there be any problem with covering the light sensor to have lights on automatically? My platinum (thought it was silver, but papers from dealer say platinum) is nearly invisible on the road, especially with the top down.

 

That thought had crossed my mind as a way round the DLR requirement!

Graham

 

I do not think there is any problem with that, other than you will be changing your headlight bulbs more often.

 

Now you've mentioned changing bulbs, is bulb life only related to total hours run or does switching on and off (as can happen often on a journey with auto headlights) reduce lifespan?

Graham

 

Thermal shock from turning on and off may reduce the life a bit, but bulb life is primarily related to total hours of use.

 

I knew you'd have the answer to this one long before I'd even thought of the question!

Thanks,
Graham

 

Perhaps I should stock up on bulbs, eh?

My current pilot-like routine includes turning the switch on the stalk to light the main lights and then pushing buttons on the console to light my fog lights (front and rear) because I'd rather replace bulbs than bumpers.

I light the fog lamps because they are so visible from greater angles.

 

Hello, had the same problem, although it was not intermittent, constant not working.
Many different thoughts on problem, about 50% said it would be the light stalk switch and the other 50% said the ambient light sensor in the rear view mirror.
Finally found out it was the sensor in the mirror for sure.
The sensor was struck in the off position.

Found the wire from schematic from sensor to stalk.
The wire is yellow with a blue tracer.

Added a relay that (tricked) the wiring into thinking the sensor was always open, basically taking the sensor out of the loop, so whenever the ignition was on, the headlights were on, essentially making them daylight running lights, which is what I wanted.

I am not the repair guy, my car audio guy did this. He used 2 relays one on the yellow w/ blue tracer and a 12 volt power source. This was all done under the steering wheel cover plate. He said it is easy fix for someone that knows wiring schematics. I would suggest getting with your car audio shop and have them look up the wiring schematic for your car and the auto headlamp sensor in mirror. This repair is definitely an "outside the box" repair, but is works perfectly.

Like I said it (wire) goes from mirror to the light stalk on steering wheel and is one wire, yellow w/blue tracer and then you need to add a power source, both easily accesible under steering wheel cover plate. But remember the car runs off a negative ground power source.

I'll bet that if WhiteXKR reads this, he will know exactly what to do and maybe able to explain it better!
He is a GURU with this type of repair. There are several threads on this very subject , but never a repair like this that I have read.
So i am hoping that there are a lot of people out there that can benefit from this thread and fix for their auto headlights not working properly. Maybe he can write a easily understood fix and create a permanent sticky repair sheet.

Please feel free to pass this on and on.


This was a five dollar fix for me because he was installing new audio, instead of the 450.00 for a new mirror. I was elated!
Good luck with repair, hope it works.

Mitchell

 

Thanks for this hint Mitchell.

Although I have not tested it, it appears to me that it can be done with one normally open single pole relay.

First, whether the auto sensor is working or not, the yellow/blue wire should be disconnected at the rear view mirror.

Any source of ignition switched power can be used to power the relay coil, such as the cig. lighter circuit. Then the normally open contacts should be connected one side to the yellow/blue wire, and the other side to ground.

This will turn on your (low beam) lights always whenever the ignition is on.

 

I thought that black bubble thing on the dash was the light sensor? I'm in an 01. My dash cover sometimes covers it up.

 

This black thing (colour depends on trim)?

JAGUAR XK8 - Solar Sensor.pdf

This is the Solar Sensor - part of the heating and ventilation system.

Underneath the dome is a a photo-diode which measures direct sunlight. The signal is passed to the AC control module which automatically reduces air temperature and increases fan speed to compensate for solar heating.

Graham

 

I read in this forum that a relay can be used to do the same thing as the sensor did. If a relay is used to replace the sensor, when the ignition is on the relay closes to ground the circuit and the headlights come on. I purchased a mini relay and installed it in the space above the overhead consol. It works perfectly. I have a 1999 XK8. The green wire is the one that needs to be grounded when the ignition switch is on and the headlight switch is on Auto to cause the headlights to be on when the ignition switch is on.


If you can get your old mirror rebuilt as some owners have been able to do that is the way to go. Keep it original if possible.

 

Hello and yes you are welcome!! :-)

Glad you were able to do this, it is significantly cheaper and easier to do and is about a $1.50+tax repair.

I have never heard of anyone doing this with the exception of me. It works perfect and will never be a problem again. Yeah.

No one would even know it was not stock or OEM!

Happy Motoring...