What is a blend door issue on 1998 Lincoln Navigator

I have a 98 Lincoln Navigator and the fan blows in all modes on the climate control. The problem is there is no temp control. I have no A/C or heat in any mode on the system. Everything else on the car functions fine but the is a check engine light on on the dash.

Asked by for the 1998 Lincoln Navigator
The temperature blend door is a door on the heater plenum in the dash that controls hot verses cold air flow. When the blend door motor, which does all the work of opening and closing the blend door and changing air temperature, fails - then the temperature will not change any more.

Sounds like this is happening for your Navigator. The only way to inspect and replace the actuator is by accessing the dashboard. I recommend a qualified technician to perform this job.