I just got a 1990 f150 xlt lariat. the last owner told me the heater wasnt working so i took a look at the heater core (i found out later that the owner before the last owner bypassed the heater core but that shouldn't matter), When i took the cover off i had to disconnect the the little vacuum line harness on the right side of it. Every since then my ac has been stuck on defrost. Also underneath the hood there is (was in my case) a white vacuum line that is supposed to go from the firewall to the little silver vacuum thing by the right wheel well. The vacuum line has been cut by someone. Is this my problem? All of the vents were working before i removed the heater core cover and that white vacuum line was already cut so i dont think thats the problem.

Any help is appreciated?