Heater stopped blowing hot air. on 2000 Dodge Stratus

I have a 2000 dodge stratus 2.5l v6, and the heater and air condition have all worked great until like almost 3 months ago. I have been running the air condition all summer long with no problems and all of the speeds have worked great. Then about 2 months after that, I noticed that the air condition would work, but only when you turned it on the high speed. Did not think anything of it, thought maybe it was just a fuse. Well towards the end of this summer I started to use my heat in which the first time I tried the heat it worked for about 15 mins, then started to blow cold air? I thought maybe it was my coolant, but I checked it and it is fine. Now the heat blows cold air all of the time, with me sometimes feeling small traces of heat coming out then going back to cold air. I dont think it is my thermostat because my temps have been fine, but I could be wrong.

Asked by for the 2000 Dodge Stratus
1 answer
If the floor outlet air temperature is insufficient, Check both heater hoses by placing your hand on the both hoses. Both heater hoses should be HOT to the touch (coolant return hose should be slightly cooler than the supply hose) If coolant return hose is much cooler than the supply hose, locate and repair engine coolant flow obstruction in heater system.

1.Pinched or kinked heater hoses.
2.Improper heater hose routing.
3.Plugged heater hoses or supply and return ports at cooling system connections,
4.Plugged heater core.
5.Air locked heater core.
6.If coolant flow is verified and outlet temperature is insufficient, a mechanical problem may exist.
1.Obstructed cowl air intake.
2.Obstructed heater system outlets.
3.Blend-air door not functioning properly. (in Heater A/C Housing)
If temperature cannot be adjusted with the TEMP lever on the control panel, the following could require service:

1.Blend-air door binding.
2.Improper engine coolant temperature.
3.Faulty Instrument Panel Control.