Cold air coming out of heaters

[Maxalfie1]

Hi, I have a 2015-2016 Nissan Navara NP300 and it’s just blowing cold air out the vents, when temp put on hottest setting. The mechanics are baffled. Radiator works perfectly, New water pump, new thermostat fitted, made no difference. Entire system bled, re bled, zero air locks. Quality coolant added. Levels all correct. Cooling lines/pipes all correct. Drives perfect, zero over heating of engine. Just no hot air coming out of vents. Air does warm up whilst driving, but only like warm, but cold only on tick over. So I can’t clear frosted windscreen, warm the truck up on cold mornings. Anybody any ideas. Mechanics contacted Nissan and they had no suggestions, over and above the aforementioned? Regards. 

[Mikildo]

I have exactly the same problem.