Highway driving and my battery light comes on. It flickers for a bit and then become solid. I am suspisious of my alternator because 2 months ago I drove rather quickly through about 8 inch deep puddle of saltwater that was about 20 feet long and seemed to have soaked my engine[8D]. The alternator seemed to begin to make a whirring noise even after cleaning and has continued to do so ever since. It has been dry here for the last month or two and yesterday I just completed a 700 mile round trip to DC and back from the east end of Long Island (without issue).

I don't want to jump to conclusions, so are there any other possibilities that come to mind besides the alternator that would turn my dash battery light on steady.

If it is the alternator, is one on a 2000 Disco II easily swapped out.

Bill

 

Don't guess on this one. Clean and tighten all you battery leads, then go to Auto Zone and have the charging system checked for free, see what this shows.
Yes the alternator is easy to replace, with your mileage, if your belt is showing it's age then replace it at the same time.

 

I had the belt changed at 80,000 when the oil pump failed. I am at 120,000. the belt does not look bad, should I change it anyway?

 

Yes, the belts are normal changed every 45,000 miles, especially since that serpentine belt drive everything.