05 Chrysler pt cruiser 2.4 dohc no heat when on defrost
 

I have an 05 Chrysler pt cruiser 2.4 non turbo . When I have the blower motor off and have the selector to feet or body it builds up temp and then I can turn the blower motor on and it blows heat through feet or body but as soon as I put selector on defrost or defrost and feet and the temp slowly drops and starts to blow cold air. I tried bleeding the system, I flushed the heater cores, changed thermostat with a fail safe , water pump and timing belt, and temp sensor and cleared engine code after the temp sensor cuz that's what the code was and now there is no more code and I did this about 3 or 4 days ago.