2001 Dodge Ram only luke warm air from heater

In my dodge ram I can only get luke warm air. Both heater hoses air hot, I have tried 2 new thermastats. I flushed the heater core with water and air. I checked the temp. Control motor under the dash. All the vacuun control vents seem to be working all right. The top rad hose gets warm but the lower one stays cool. It almost seems like I am drawing too much cold air from the outside. I am stumped. Any suggestions?