2003 Jeep Cherokee Heater intermitently blows hot and cold

Once the motor is warm it is warm so the antifreeze cannot change back to cool, that being said. I dont know how fast the change is happening but if the heater core was clogged up partiallly I would think it would get cooler but not cold once hot, not that fast anyway? You may have a door opening and closing. One that is allowing outside air to be blown in and the when it closes it picks the heat up from the core. When the temp is fluctuating try and see if a door is shutting on you. Also you may try and blow through the heater core to remove any debris? A flush and fill may not hurt either. Hope this helps. Curt

Thanks Curt. I'll give that a try.