GCL ac issue

My 2002 GCL blower works but only from the defroster ports under windsheild, not the passenger or floor settings no matter where the switch knob indicates. Speed of blower seems fine but air does not come out the vents ....any ideas

There is probably a vacuum leak or a vacuum line that is unplugged somewhere.
The ventilation system uses vacuum to actuate diverter valves which control the flow of air.
If there is no vacuum, the system is designed to default to the defroster position, for safety reasons.

Thanks, where would I begin to look for the vacuum lines