Ok, so I recently purchased a '96 Blazer for $800 and it doesn't have to many issues. However I was having no air comming out from the blower when I purchased it. So I replaced the blower motor relay and the motor started blowing but only on the high speed. So I also replaced the blower motor resistor because that controls the heat, but the 3 lower speed still dont even work. Also, the air that comes out isnt even hot, sometimes it will be a little warm but thats it, I have recently replaced the thermostat as well. I hope its not the heater core is there anyway to trouble shoot these heat problems? Thanks!!!!

 

Could be a blend door issue for the heat.

As for the fan, check the voltage going to the fan when you have the switch set at certain settings. Could be an issue with the switch.

 

I actually replaced the blower control switch on the dash and it didnt change anything... what is the "blend door"?

 

Still wouldnt hurt to check the voltage going to the motor on different settings. That will tell you if its the motor or something leading to the motor.

Blend door is the door that controls the mixture of air going through and bypassing the heater core.
Can always check to see if you can feel coolant flowing through the two lines to the heater core when its warm, and also to check and see if both lines are warm.