My mother-in-law has a 1999 Chrysler Concorde with a 3.2 motor. When she turns on the cars heater it blows nothing but cold air. I just replaced the thermostat last night. The fan/blower works in all different speeds and settings. Engine coolant is fine, and the cars temp rises and stops at it's normal temperature. Need help!

 

Did you bleed the cooling system at the vent? Most common cause of no heat in these cars. As little as 1 quart low = no heat.
Bleeder Screw, looks just like a brake bleeder, in the center if the intake, just behind the upper hose area. 3/8" wrench size (not metric).
Cold engine, Overfill the reservoir using a snug fitting funnel, with bleeder open. Helps to "massage" the upper hose to gat as much air out as you can. Snug the bleeder, cap the reservoir, start the engine, as it warms crack the bleeder just enough to let the bubbles out. Run to full temp, top coolant AFTER Fully cool, like next morning.....