Cadillac: No heat or AC, vacuum lines, dash lights

Question
i have an 83 coupe deville and the heat does not come on when the climate control is changed to heat or ac. You can hear the blower come on and the speed changes on lo, hi, auto and economy. I am in the process of changing ac compressor because there is a diode across the plug for it which i know shouldnt be there. Just trying to figure out why no heat?

Answer
That diode MUST be there or it will cause dash lights to blink ZON and OFF.

Your fault for no heat or AC is most likely caused by the AC/Heater PROGRAMMER located behind the glove box on the passengers side and has several different color vacuum lines attached to it.