while idling my interior heat goes cold but heats back up when moving. why?
on 2010 Nissan Xterra

At a stop light my heat-air coming out of the interior vents go cold and warms back up when I start moving again. The Heat gauge is in normal operating range and coolant level is normal.

Asked by for the 2010 Nissan Xterra
Check your coolant level and top off as needed- both the resevoir and the radiator itself. If you find the level very low (more that a few quarts) top off with the proper coolant and get your vehicle's cooling system checked for leaks.