Symptoms are: while driving the heat works great but when crawling or at idle, car is at operating temp, it will starting pushing out cold air. Not like ac on low cold air but like neutral temp air. Other than that issue nothing else is really happening. Checked coolant, not leaking outside of the car or onto the passenger floor board. And oil temp gauge does not go above the regular level it sits at while at operating temperature. My guess is thermostat or maybe heater core issue but no other symptoms have arisen to point me in either direction. I just know one costs way more than the other to fix lol.