A/C and heater problems

Hi everybody, I have a 2000 dodge ram 1500 and I have a few problems with the A/C and heat. First off, a while back I believe my old mechanic had said my heater core was leaking so he had did a temporary fix by linking the 2 hoses together and bypassing the heater core. Well, I had totally forgot about it and now that it is getting colder outside I decided to hook the hoses back up. It isn't leaking any coolant on the passenger's side floor but I do have smoke coming from the vents with a weird smell to it so I am assuming the heater core is bad which I plan to replace. But here's the deal, my a/c worked great when the heater core wasn't connected but once I hooked it back up, it doesn't work now. I have air coming out still when it's on the a/c coldest setting but it's hot air. Kind of strange? Why would the a/c stop working even with a bad heater core? Also, the defroster only has air coming out of the drivers side but not the passengers side. Does this whole thing sound like a blend door problem? Thanks for any advice.

If your system is vacuum operated, you probably broke loose a vacuum hose or connection under hood. Heater core change will a dash pull, so a/c will get disconnected anyway. All mode and temp door operations can be checked when HVAC module is sitting on your workbench.