EATC low speed heat, high speed no heat

took the car out today back and forth to work.
notice that my EATC works good but for some reason if it put the fan on high i get cool air, but then when its on low i get lots of heat.....
im asking this because i have had this before but never fixed it, it went away or summer came...
really sad though, since that i work on car's everyday and haven't been able to figure it out, and quick ideas on why this is happening???

BTW i gotta take the dash back out cuz i think the blend door motor is going to die, it make a wonderful clicking noise when it moves., but i keep it on 90* now, lol
any help would be great.....

i miss driving this car, rod knock and all still lights those tires up when told to,

also 50w oil doesn't really effect turn over speed of starter, but does it draw some current glad i running two 65 series interstate batteries

The blend door may not be moving and the clicking is stripped gears. Heater core could be plugged up not allowing enough hot water in so when you put the blower on high the air flow cools the heater core down or the blend door is only partially opened to the heater and when you use high the amount of cool air bypassing the heater overwhelms the warm air. The ambient temperature sensor could be bad. You should get the codes.