My recently purchased 84 Sedan had an issue where the climate system, once set to 65 or 70 degrees would switch between full cold to full hot from the dash vents only. Thinking it was the in car temp sensor on the air box or possible programmer I watched the system with the glove box liner removed. For no apparent reason the blend door arm would move back and forth within 10 min of use maybe 3 times. I replaced the programmer and adjusted the blend door arm per the FSM and it works perfectly. Warm air this morning with ambient at 67 degrees, dash setting 74 degrees and from the floor vents! Yesterday with ambient at 81, settings at 74, it blew cool air and the fan reduced speed gradually as its supposed to do. Thought this might help others.