Low water level in the upper tank, is what I discovered.  In the case of our '87 it meant that the hose between the upper tank and the lower had frayed and cracked on its top side so that the hose now acted like a trough instead of a straw, allowing water to exit the upper tank when warmed up but once cooled down the vacuum leak caused by the crack in the hose would not draw the water back from the overflow tank to the upper tank. Check your water levels in the tanks and look for a leak in that hose or one of the plastic nipples it attaches to.  There may be other causes but this is what I found on mine. 
Stephen   

    On Thursday, January 5, 2017 4:35 PM, John Rodgers <jrodgers113@GMAIL.COM> wrote:
 

 What does it mean when that light turns on without blinking. Solid red.
Stays on. Engine does not get hot. Temp needle never moves off of the light
spot once it's warmed

Whats up with that!

John