Heater is not blowing hot air on 1996 Dodge Stratus

My heat is barely blowing hot air. It's just warm enough to defrost the windows if I leave it run for awhile. If it sits idle for 10 minutes or so it will blow hot air but I start driving and it gets cool again. I checked the thermostat and it is fine. Need some help please!

3 answers
There is a temperature blend air door, it is operated by a cable attached to the heater control lever. Check the other end of the cable, there is a plastic lever that sometimes breaks, if it's broken, it will need to be replaced.
Check your water pump.
mine done this and i took heater hoses off and backflushed heater core until it was clean and it works fine now