My 2003 ML350 has a problem with front defroster.
Blower works fine, but when you hit the defrost button on dash, it does not operate the flapper door ducting to make air come out at the base of the windshield. Air blows out the two ducts on each side of the dash but none at windshield base. Turn defroster off and direct air to the windshield, air come out center duct and none at base of the windshield. Anybody with ideas? Has anyone had this problem before?

Thanks in advance for your help!

 

Same with my 2004 Inspiration - got plenty of blower power, but none coming out of the windshield vents.
I don't get the 'ticking' sound that may indicate a drive sleeve problem.