My 2WD 1993 V6 3.0 automatic transmission sometimes won't go into "L" gear. Fluid is full. It happens more often when engine is hot, less so when cold. Also the green back lighting is sometimes dim and sometimes bright, that goes for all the gears.

 

Have you checked for codes?
http://web.archive.org/web/201408161...31diagnosi.pdf

On open #1 solenoid should throw a code, but you might have an intermittent problem.