Baring Ford did not change the component layout and operation for 2008, its more than likely either a bad vacuum control motor that controls the floor/panel door, a vacuum leak in the yellow vacuum supply line to this motor, or a bad vacuum function selector switch.
You can try to narrow it down by visually watching the vacuum motor as you switch between panel vent (no vacuum to either vacuum lines at motor) to panel/floor (vacuum at blue line) to floor (vacuum at both lines). The motor should move from full extension, half way, fully retracted. If not, try removing the yellow vacuum line at the motor and checking for vacuum with the selector set to floor. If no vacuum is present, check for a vacuum leak in yellow line between the motor and selector switch. If no leak is detected, replace the vacuum selector control switch.
2001 Ranger Edge 3.0 V6, 5 speed M/T
Limited Slip Differential, James Duff Traction Bars
Kumho 30x9.50 15 MT / Black 297 Series 15x7 Rims
Last edited by Rev; 11-18-2014 at 11:25 PM.