I have a 91 xjs and the light on the passenger side door turned on and won't turn off. Any idea what is wrong?

 

Have you a switch on the dash ?

 

Door light switch contacts can be cleaned with contact cleaner spray or fine Emery paper



If you mean this light it's controlled by a switch at the front of the door.
When the door closes it pushes the switch in, switching light off.
Sometimes a sticking switch can be rectified by pushing switch in and out with your hand.

 

Both door lights are commoned so either door switch will switch on both lights.

The lights are switched on by the switch shorting the Purple/White wire to ground. If this wire was shorted both lights should be on.

If you pull the light out of the door check the P/W wire it may be broken, or the terminal pulled out of the plug and shorting to the door frame.