My 97 Montero Sport blows cold air. on 1997 Mitsubishi Montero Sport

My truck blows cold air when the rpms are below 2000. The blower motor works. I tried changing the thermostat and that didnt fix it. Fluid levels are good. I dont understand what else it may be. Please help.

If you are not experiencing overheating problems, then it sounds like your blender vent is stuck or broken behind dash need to check and make sure that vents are changing when you change flow locations and then check blender vent door.