my ford mondeo heaters r only blowing cold air?

my ford mondeo r-reg 1.8TD heaters are not blowing hot air ,i have changed the thermostat twice know all the pipes are hot, the temperature gauge rises to about half way ,just under.....if there is a air block i dont know how to remove it,or is it something else please help......
olly.p., December 2006
You'll probably find that the control to the mixer flap on the heater box is faulty generally caused by a broken cable from the heater control panel to the mixer flap on the heater box.

Ian, December 2006
link Click here to see other fixes for Ford Mondeo.