Rep Power: 0

1993 civic si. I recently took out my dash and replaced the heater core. I put it all back together but now I get constant warm/hot air blowing. I adjusted the 2 cables on the bottom of the heater box but it doesn't really blow cold anymore. I used to be able to drive with the setting on cold and I didn't need AC. Now with it set on cold, it blows hot out the left driver vent and kinda cold in the center and passenger side. I remember there used to be a thud when changing between vent/foot/defrost but no longer there. What makes the blend door move?

 
Rep Power: 210

Could be:

Faulty heater core internal temperature control sensor
Faulty water heater valve or cables leading from climate control to the water heater valve.
Faulty blend door solenoid/actuator.

The heater core internal temp sensor looks like (but isn't) this: https://www.hendrickhondaparts.com/o...CABEgIXtPD_BwE

Check the heater valve's rotating arm to see it moves when you move dash climate control from hot to cold. At max heat the water heater valve's arm should be closest to firewall. At max cold should be pointing towards engine.

Chech service manual, google search or check you YouTube on how to test the blend door actuator motor.