The A/C system of the Ford Escape has a resistive sensing element used regulate the blower motor. If you find that the A/C blows air on some fan speeds but not others, it is likely that the blower motor resistor has burned out or otherwise failed. On my 2009 Escape, the blower motor would run in positions 3 and 4, but not 1 or 2. Based on other reports online, failing for the low speed settings seems to be the most common symptom.