What may be causing burnt smell coming from under the hood?

Hello, What is likely happening is that oil or coolant, you can tell by the smell, is leaking onto the exhaust manifold, or another hot component. Most times, burnt oil smells come from the valve cover dripping. A big thing to remember is that yes, the heater was on, but so were all of the other components of the vehicle. Let me know if you have other questions, otherwise, here is a list of certified shops for your convenience. http://repairpal.com/dodge-within-10-miles-of-fayetteville-arkansas-72703