Heater problem

[NavigatorV8]

in the morning time, if my heater runs with full power, will happen the following sometimes:
after several miles, suddenly the vents blow cold air in the cabin. After pressing of different switches at the DATC the vents blows warm air again.
But not always, sometimes everything is okay, sometimes this fault.
What can it be?
It´s a Navigator from 2004

 

[tixer]

Is it possible that this is "normal" operation? If I set any of my Lincolns to maintain a specific temperature, the system will cycle between warm and cool air as a means of doing so. Next time this happens, just adjust the temperature to be 1 or 2 degrees warmer and see if you start getting warm air again within 30 seconds to a minute.

If the air stays cold until you switch between modes, I might be suspicious of the EATC itself.

 

[NavigatorV8]

thank you for reply. In the morning time, i set the temperature in the highest level and most in the vent air condition

 

[chris2523]

i don't know enough to be certain, but other fords of this era have had issues with the dual climate control valves. does the navi have one of these? or other similar valves in the coolant heater core loop?

 

[NavigatorV8]

where can i find them?