Electrical diagram 2000 jaguar xj8

https://www.corvetteforum.com/forums/c6-corvette-general-discussion/1700828-help-rearview-mirror-lights-won-t-turn-off.html
This forum from corvette may shed some light on what to do.

If the car had power to the mirror the harness is probably tucked behind the headliner above the mirror.

Usually it is in the drivers window controller.There is a module that usually goes bad.

Could have a DDS an PDS .depends on what RPO code yours has >
Outside Mirror Description and Operation (with RPO DL3)
Or
Outside Mirror Description and Operation (without RPO DL3)
Without
Heated Outside Rearview Mirror Operation
The REAR DEFOG relay controls the operation of the heated outside rearview mirrors. When rear window defogging is requested, the REAR DEFOG relay is energized and B+ is applied to the supply voltage circuit of the mirror heater element, located in the mirror face. A constant ground is also applied to the mirror face. Current will pass through the mirror heater element, warming the mirror, so long as the rear window defogger is commanded ON.

With
Heated Outside Rearview Mirror
The DDS and PDS control the activation of the mirror heaters. Upon receiving a serial data message indicating a request for heated mirrors, the DDS and PDS, will apply voltage to the mirror heater element supply voltage circuit. The mirror heaters will remain active until a new message is received indicating rear defogger is to be deactivated.
The power mirror system consists of the following components:
• Driver Door Switch (DDS)--An electronic control module with integrated switches and requires programming when replaced
• Passenger Door Switch (PDS)--An electronic control module with integrated switches, requires programming when replaced
• Power Mirror Direction Switch--Integrated into DDS and is a four position momentary switch that provides a signal input to the DDS for up, down, left/extend and right/retract with a mirror switch activation
• Mirror Select Switch--Integrated into DDS and is a three position switch that allows the operator to select the left or right mirror and also a neutral/fold position
• Mirror Extend/Retract Switch--Integrated into DDS and is a two position switch that allows the operator to select the mirror extend or mirror retract position
• Left Outside Power Mirror--Contains both the vertical and horizontal mirror motors
• Right Outside Power Mirror--Contains both the vertical and horizontal mirror motors
• Body Control Module--An electronic control module that requires programming when replaced, serves as the power mode master and is the main message handler
• Horizontal and Vertical Position Sensors, if equipped with memory mirrors--Supplied a 5-volt and low reference by the DDS/PDS and provide a variable voltage signal to the DDS/PDS that is proportional to mirror position
• Folding Mirror Motor, in each of the outside mirrors, if equipped with power fold mirrors--Provides extend and retract movements of the mirror and is serviced as a complete mirror assembly
Your best bet mite be to take to a qualified repair shop , i really don't think you'll be able to do anything with it.
Do you have wiring diagrams so you know which wires to test ,do you know how to do electrical testing ?
The Driver Door Switch (DDS) and Passenger Door Switch (PDS) supply voltage to the outside rearview mirror heater elements upon receipt of a serial data message from the HVAC module indicating that the rear defrost system is active. The door switch supplies B+ through the driver/passenger mirror heating element supply voltage circuit when a request is seen. Ground is applied through the driver/passenger mirror heating low reference circuit.

yes any vw mirror will work.

If this is the light that is controlled with the center switch, it can easily be changed by carefully prying the plastic cover off and replacing the bulb, found at any local auto parts store.

ck interior light fuse (10 amp) make sure the dome lamp is not in the OFF position. with the mirror, the outside temp sensor could be bad or disconnected. the sensor is near the front grille, in front of the radiator. a little 2 wire sensor. if it has been wrecked, maybe it did not get put back on.

I had the same issue...I went to Auto Zone and got a diagnostic...Came back that my Throttle Position Sensor was faulty...However after taking it to the dealer, and paying 135.00 for THEIR diagnostic...You can't simply buy the sensor. You have to buy a new Throttle Body at 902.00 + Tax atleast here in Vegas. I hope it's not your problem, but go get a FREE diagnostic first.

Check the electrical grounds for the taillights. In fact, get a diagram and check all the easily accessible grounds. Many of these are in the engine bay.

Dan

Hiya...ALL factory-installed rearview mirrors are installed with different wires due to options.
About 6 different rearview mirrors are installed with those options such as On-Star, light, compass, and those features which use different wires....THIS CANNOT be modified with different rearview mirror....**for example, the Equinox owner attempt to pull out a factory-installed base rearview mirror and put in different one that has compass/temperature built into the rearview mirror**

However, the wires are located inside the front headliner which requires removing the sunvisor (and possible removal of interior plastic trim part at the left/right ends of the windshield) prior to pull the headliner down, and a small metal philips or torx screw is used to secure the rearview mirror onto the bracket glued to the windshield.

The best solution is to leave the original factory-installed rearview mirror in place.