Vents won't work...

I have an '02 Explorer with a 6 cyl. engine, 170,000 miles. I am having a problem in that I cannot get the dash vents to function. The blower works fine on either A/C or heat, but I cannot get the air to blow out of the dash vents. The defrost vents, foot vents, and small side window vents seem to work fine.

One suspicion would be a vacuum line has become disconnected, but I'm looking for possibilities. If it is a vacuum line, where should I look to see if that is the problem? Any other thoughts on what might be wrong?

Vacuum line would be a good suspect if you have the manual HVAC controls. If you have the EATC, the problem may be electrical, but the EATC has self diagnostics.

-Rod