NEW NOTE: I replaced two vacuum hoses during the engine replacement. Could I have connected them wrong ? Could it be a vacuum issue ?

I have a 99 4WD Blazer. Replaced the engine myself last weekend and now hot air blows all the time in the vehicle, even with A/C on. Did I cross the heater core hoses or something else ? Must be related to the engine replacement, but the Blazer runs great now except for the hot air. Thanks, thanks, thanks in advance.

 

My heater in my 96 blazer heater is giving off heat all the time also after I accidentally left interior lite on and ran battery down. Air conditioner now when turned on blows heater air also. Checked fuses, and don't know what else it could be.