As the title suggests I have succesfuly replace my heater core evaporator core and accumulator in a 2001 blazer 4door. However I now cannot control the direction of the vents nor the temp (although the temp was originally caused by a sludged up core). after completein the task I have two connectors that i cannot account for where they attach to. The one in the interrior is on the passenger side Black rectangular shaped clip with two stacked rows of 8 female ports coming from the firewall near a yellow clip and to the left of that huge 3 square inch block of wires. I streched it every which way to deduce the where it may connect to but to no avail.

 

Do you have Automatic Climate Control (sounds like you do)?

Did you remember to connect the temperature door actuator on top of the HVAC box? It is under the passenger side speaker, somewhat accessible when you drop the glove box down and out of the way.

The clip you are talking about sounds like the main vacuum supply connection to the HVAC control module (separate from the HVAC control head on the ACC models and is mounted to the front of the HVAC box).