Satisfying small project, about $10 all in.

I used a small 12v buzzer from Radio Shack...I lost the part number, dang it. But just Google "!2 volt buzzer" and you'll have lots of choices.

Also needed is a generic "ice cube" type accessory relay. You want the 5-pin type with terminal designations of 30-85-86-87-87A.

I used small piece of wood to mount the parts. Not very elegant, I know. But, sometimes we make do with what we have. I mounted it behind the LH foot well kick-panel.

Connections as follows:

Terminal 85 -- 12v switched power. I tapped into one of the white/pink wires at the 'load relay

Terminals 86 -- ground/earth

Terminal 30 -- 12v from the headlight switch. I tapped into one of the red/slate park lamp wires

Terminal 87A -- connect to the buzzer red "+" wire

Terminal 87 -- not used

The black wire from the buzzer goes to the purple/white wire coming from the door jamb switch; easily accessible in the bundle of wires exposed when the kick panel is removed.

Works fine. Buzzer sounds whenever the door is opened with the park/head lights are on....unless the ignition is on as well, in which case there is no buzzer.

When taping into the purple/white wire don't go too far downstream as you might end up on the wrong side of a diode...which might bollix things up. I can't remember where the diode is in the harness but if you tap into the wire in the area of the lick panel you should be OK

An abbreviated version of the warning buzzer can be made by eliminating the relay. In that scenario the black wire from the buzzer goes to the purple/white wire. The red wire from the buzzer goes to the red/slate wire. The buzzer will sound when the lights are on and the door is open, even with the ignition 'on'.

I did this on my Series III. I suspect it'll work just as well on earlier models and the XJS as well

Cheers
DD