When I switch the fan modes, all of them work except for the front defogger. There is no air been blown through the vents which defog the front windshield. The motor does work for the rest of the vents.

What should I check?

 

Opps...I meant front windshield

 

Have you had any luck with this? I have a 99 TL with the same problem. Plenty of heat/AC, plenty of blowing power, however I cannot get it to change to the defogger. I've changed the devices that open/close the vents, I forget the name, but they're near the floor and under the center of the dash.