Hi, I have a 2012 XJL Portfolio and lately we have been experiencing a long high pitched beeping while driving then our dash, a/c, display will completely shut off. On top of the brake light occasionally wanting to work. It will flash on and off when starting the engine but it rarely stays on. I live in Texas so I need my A/C to work consistently! :) please any suggestions would help at this point. We did unscrew the taillight and to see if the wiring may be bad, however I do not believe that is the issue here.
Also where can I get a diagram of the fuse box to check the fuse?

 

Ladybella23, first off, Welcome to the Forums. Lots of helpful people around here that will help solve your issue. I think you will find us a friendly bunch. But, we do ask one thing from you, please stop by the New Member section and tell us a little bit about yourself and your car. This will help introduce you to those that make this place move.

As for your issue, I think what you have is a failing fan in the dashboard. If you look at the overhang for the instrument cluster, there are a lot of vents there. Inside that area, there is a fan that is blowing cool air into the dash to help cool the instrument cluster and the radio screen. If this fan starts to fail, I can see where it would start making a high pitched chirp. With the loss of air flow, this will cause the screens to shutdown on high temperatures.

As for the brake light, I would be checking the switch under the dash where the brake pedal touches the switch. There have been instances where this switch will become loose (foot kicks it, just wiggles loose, etc) and it will cause the brake lights to do funny things. Sticking your head under the dash and looking up, you will see the switch on a mount next to the brake pedal bar. If it is not that, then let me know. You can download a set of diagrams from this site. If you look above, there are what we call "Stickies" (things that remain at the top of the page for each vehicle). These are important things relating to the car and for the X351, we have a repair manual and wiring diagrams up there for you to download. This may provide some assistance. If you need wiring help, let me know. I do electronics for a living and will be able to explain things down to a level that you can understand. Just let me know if you have a multimeter and if you know how to use said multimeter.

If you happen to live in the DC area, I would tell you to come over to my place so we can see what is going on. But, that is up to you should you live close.

 

Until the car is properly scanned we just don't know?
Can you get it scanned with the factory SDD?

As Thermo mentions this car is VERY complicated and even provides cooling to the back of the dash board and the center navigation stack.
But all of this sets codes because it's too expensive to just start changing parts.

Sometimes that technique is called "Loading the parts cannon" because you are just shot gunning the repair with out proper diagnoses.
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