Just replaced my heater core today and after hours of work I get everything back in and what not, start the car up, and there's no air coming out of the defrosters...though I can hear it, it just doesn't come out of the vents. It comes out of the regular vents and the lower foot vents but not the defroster vents. Anyone know why this would have happened? Also the fast cam idle switch decided to just stay up now even after engine reached normal operating temp, had to push it down manually. Thanks.

 

Check vacuum lines for the vents