I just took to my new to me XJ8L on a 2000 mile round trip vacation. Everything worked perfectly except the automatic headlights would randomly come on and go off during the daylight hours. I can't find anything that tells me where to begin troubleshooting this problem. Are the sensors for this in the rearview mirror or on the dash? Any idea where I can find a wiring diagram so I can trouble shoot the problem? I can just use the headlights manually but I would prefer to repair the problem.

I really love this car. It rides smoothly and quietly, has lots of power and got 31 mpg on the trip with 3 people and luggage. My only problem in owning it so far is the information I need to repair it is hard to come by.

 

The sensor is in the front middle of the dash, but this fault may not be the sensor, but the lighting switch on the steering binnacle. Do you get any flickering at night with the lights on ?

 

Fraser,
There is no flickering at night when the lights are needed. It only occurs during daylight hours and may not happen for an hour and then does it on and off for a while until I shut the lights off for a while and then turn them back on. Then they will not bother for a while but once it starts it will continue until the lights are off for a while. I have 2 sensors on the dash. One is close to the windshield and the other is maybe an inch back from it. Which one is for the lights and what does the other one do?

 

Sounds like it's not the switch if the lights are OK at night. As for the two sensors, I think the rear one is for the daylight detection, the other one, towards the screen, flashes red when the car is locked and alarmed. However don't take this as gospel as I have never needed to know which is which so far !

 

So after cleaning the sensor and having the problem reoccur again I decided to take the sensor out and test it. The sensor and the security light are mounted to aplastic part that snaps in place. The bad news is that the plastic had become so brittle that the little ears broke with very little pressure. There are metal clips attached to the the plastic ears that fell into the cavity along with bits of the plastic ears. I contacted the nearest Jaguar dealer and order a new sensor and a new plastic mounting piece. Total to my door around $156.00 I installed them to day and hope that is the last of that problem. That will take a few days to verify as it was an intermittent problem.
The lesson for anyone wishing to take the part out is to be prepared to buy a replacement plastic part as well as get a magnet to fish out the metal clips from the cavity so you can reuse them.

 

It appears to have been caused by the turn signal Stalk. I replaced it with a used one and all is well now.

 

Just as I expected. These switches are well know for failing and some very odd things happening as a result.

I had a new one fitted about four years ago, and no trouble since.