My 1994 Jaguar XJS;
The interior lights work if you have locked and unlocked the car by the remote. Or if you start the car they will work for a period of time then the next time you open the door they don't. The trunk always works. Sometimes if you close the door upon entering, lock it. when you open the door they work. sometimes not. Sometimes when I use the remote it makes a last beep sound then they work. No beep they won't work. Once I get them to work I can go out for about two hours to check-they work. overnight they don't. The battery is new and is kept on a battery maintainer. If I unhook the maintainer it makes no difference. It is stored on in a climate controlled garage kept at 45 degrees. I'm totally stumped. If I have to send to a service it could cost $$$$.

 

Go to the website below, and download the wiring guide near the top of the page for your year and model. Diagrams are there for the interior lights and security systems. There is a control module for the interior light delay, and also a relay in the circuit. Maybe one of them is acting up.
JagRepair.com - Jaguar Repair Information Resource