OK....

When I have my heater set to defrost, it blows warm air and doesn't defrost all the way. If I switch it to vent (directed toward driver/pass) it only blows cold. I can try to mess with the temperature slider but it does nothing. Is it my Logicon or my heater?

 

doesnt sound like the heater core to me
logicon i am not sure

but i do have one for sale $20 plus shipping

 

I think it's the motorized arm/door that moves when you move the hot/cold slider. You should be able to hear it move when you make sweeps back at forth right about the inbetween hot/cold.