I got a 1999 dodge Durango slt wit the 5.2l. I have no heat unless I turn the blower off or on lowest setting. I replaced the thermostat it has a new water pump and radiator as well as hoses. I don't have any leak in pressure, no puddle in passenger floor. It is in good range on mixture as well as coolant level. Any ideas?

 

Start by flushing heater core with hose. There is a good video on youtube.