Jaguar Repair: alternator light, tracer wire, volt meter

Question
I replaced my lucas laternator on a 1988 XJS V12 5.3 It seems to charge fine. I drove it around town for a bit. It was fine. THen took it on a one hour trip and when I parked it, as I turend the key off, the charging light came on and stayed on with the key OUT. I turn it on, and teh light goes out. I take the key out, and the light goes on again. Any ideas on what to look for?  Thank you! David

Answer
Hi David,
I don't work on any Jag after 1987 but I happened to have a wiring diagram of the 88 XJ-S and I see that you need to disconnect the small brown w/black tracer wire on the alternator when the light is on and the key out. Then use a volt meter to test the end of the disconnected wire and post on the alt. to see which has voltage on it. If the post has voltage than the alternator needs to be repaired or replaced.
But if the wire has voltage on it, you have a big job of working with a diagram and a test light or volt meter to see why that wire has voltage on it when it is not suppose to.
Howard