Thanks.
I did have him hit the same switches with contact cleaner this
afternoon.  I'll check that switch in a few.

thanks for the info.

The instrument panel lights have a knob that adjusts their intensity, when
fully to the BRIGHT setting, there is a detent that turns the dome light(s)
on.

I suggest you go over ALL of the linkages that you applied WD40 to, and
apply a liberal dose of solvent to clean the WD40 away. WD40 is good -- sort
of -- to free sticky parts, but when WD40 dries, it becomes another gooey
mess that you will have to get rid of. WD40 is not a lubricant, and it will
cause far more problems than it solves if you leave it in place.

Odd problem with a '99 Ranger my son bought the other day.  

The Door Ajar light was on solid and the previous owner had pulled
the dome light fuse.  WD-40'ed the door switches and the Door Ajar
light now works as it should, but the dome light still remains on
constantly with the switch in any position.  Moving the switch
slowly from right to left, I can find a "sweet spot" where each
one will turn off individually, but in any of the actual switch
positions, they remain light no matter if the doors are open or
closed.
I would have assumed that the dome light was controlled by the
same switch the Door Ajar light was.
Am I missing something obvious?