Hi All. The auto-headlights on my XK8 have not been functional since before I bought it. My first question is whether or not there is a way to determine whether it is the headlight switch or light sensor in the mirror? The next question is, if it is the sensor, can that be replaced or repaired w/o replacing the whole mirror? For information, when I am rotating the light stalk, the first two settings work fine, and when I get to the auto setting there are no parking or main lights. I have also tried putting my finger over the sensor with the stalk in auto with no results. Thanks!

 

First thing to do is check that the mirror hasn't been replaced by a previous owner - he or she may have replaced it with a three wire mirror.Take off the dome lights and look at the connector - if five wires are coming out of the mirror then it does have an auto headlight function. Then check the wiring diagram on Gus's site applicable to your year - one of the wires carries the autoheadlamp signal - can't remember which one and I'm away from home at the moment. Try completing the circuit on the applicable wire(Check the schematic - not sure whether it grounds or goes live to complete - be careful). If the lights come on that points to the fault being in the electronic panel in the mirror. I'm not aware of anyone who repairs that circuitry - to my knowledge Sybesma do not.
You probably already know that the mirror sensor facing forward is the ambient light sensor - the rear facing one(i.e. towards the back of the car) senses lights behind the car. Out of interest is the mirror autodimming functional?