A/C through the defroster vents only???

Any input on this would help.

I replaced the heater core......what a pain!!! Seemed like all went together well, but I am now only getting air of any type through the defroster vents
No matter where the control is placed whether it is defrost, heat, mix, air,vent or max the result is the same.......

Need some ideas. Thanks

1998 Ford Expedition
4.6 Liter
4X4

If it was working correctly before the repair, you probably have left a vacuum line off one of the door actuators causing it to default to the defroster position. Or there is a crack in one of the plastic tubes allowing vacuum to escape.

Any idea on on the what or where of the offending line???

Sorry, but there is no way to pinpoint the place of leakage. it is a matter of checking all the lines and connections for looseness or broken lines.