Heat

What would cause it to blow hot air for heat as you're going down the road but as soon as you stop it blows cool air

Check the coolant level, it sounds like it's low and may have air in it, wait for the engine to be cold then check the radiator not the reservoir. Fill the radiator as full as you can get it then fill the reservoir and with any luck you won't need to belch orbleed the air out. I hope this helps

Does anyone no what the foot long u in between the grill and radeater is