Heater won't blow hot air on 1999 Dodge Ram 2500

Heater won't blow hot Blower fan is fine just not hot (Almost as if the AC is on) air AC works great just bought the truck 3 weeks ago

Asked by for the 1999 Dodge Ram 2500
Is the engine completely warming up? The first things to check are: is the heater control valve opening all the way? Do you have the correct thermostat installed? Is the blend door stuck or not operating? Did the previous owner remove the thermostat or even bypass the heater core for one reason or another? These are just a couple places to start.