Often the heater tap fails, it is located under the inlet manifold if the vacuum line is off the tap should be in the on position, also check that the heater core is not blocked, start here.
October, 21, 2012 AT 4:37 AM
Hi mate there can be couple of issuses can be HIM module control shaft an A/C flaps inside the dash also sometimes the shaft pops out from the HIM control can be checked without taking the dsah out remove the glove box u hav to get in with a light an see if the shaft is in the HIM control then on the AC an see if the shaft is moving also check if the air coming out is different or same from the vent if different the the shaft or the falps broken then dsah needs to come out to replace the shaft an flaps also sometimes needs to reset the HIM which need FORD test gear
November, 9, 2012 AT 1:54 AM
My heater also didnt work (air coming out cold) so I replaced the thermostate $20 (easy to replace)and it turns out it was faulty now my heater works great. Hope this helps.