2011 Nissan Pathfinder provides heat only sporadically. I have the temp set to 90 degrees and only occasionally get warm to extra warm air. Usually gets hot air when fast acceleration from dead stop. Could it be low coolant? I did check and was just about at the minimum line on the reservoir. Pulled radiator cap and coolant did not cover the top of the vanes. Any thoughts? Anyone? Happy Holidays and Merry Christmas!