Is the front blower working at all? I had a similar issue where my front blower would not blow air (hot or cold) at all, but the back blower was working fine. It turned out to be the Blower Resistor, which is located below the glove box. It was two screws to take the cover off, and two to take the resistor out. It cost me less than $25.00 at autozone, and took less than 20 minutes to replace.