the battery was replaced and maybe the positive lead was taken of vs. the ground lead. Would that cause for Heat not to blow out?
by Visitor in Austin, TX on November 25, 2010
The A/C system may need to have the system re-calibrated after disconnecting the battery. (Doesn't matter which cable was removed)
The vent and temperature controls are controlled by little motors and these motors are what need to be calibrated.
How do you calibrate the motors
It varies by manufacturer, and I'm not sure how GM does it, sorry.
You can try getting a repair manual: