I just replaced my heater core last year

The ac is controlled by the ac programmer it has the motor that controls the door. Sometimes the gear strips and u hear a grinding noise. Remove the glove box liner. U will see the rod going to ac door. Run the temputure go from 60 to 90 and watch to see if the motor is operating.

Sorry our site has been down. To test the thermostat remove the top hose at the radiator. Remove the radiator cap and stick a hose in on medium speed. Start the car if the water keeps flowing out of the upper hose then you have no thermostat in. If not Let it run the engine will heat up then the thermostat will open. You will see water coming out of the upper hose. The hose automatically refills the radiator. If The thermostat is working properly water will come out of the upper hose then shut off them in the motor heats back up again the water will come out of the top hose again. Then you'll know the thermostat is operating properly. Then reattached the upper hose and filled the radiator up and the overflow jug. Restart the car with the radiator cap off. You will see the fluid in the radiator starting to go up and down. Then when the thermostat opens you'll see the water level drop in the radiator. As you rev the engine up look in the radiator you should see water flowing through the radiator core. Then just fill the radiator all the way up. Then check the coolant jug level.