Is this the rear-window defrost switch (hence the LED in it)?  Put your
tongue across the leads on your defroster with the switch on and off-
that'll tell you if it is the defrost!

My 84 has 3 switches: headlights, hazard, defrost.
Hope these helps
Matthew

Matthew Pollard          "Racing with the wind and flirting with death
Dept. Of Chemistry        So have a cup of coffee and catch your breath"
University of Idaho
www.uidaho.edu/~poll7356