If I remember correctly, there is also a knob marked "AC" hanging from the dash, just to the right of the steering wheel. On my '48 Frazer, the sheath for the cable broke loose so when you pushed the "AC" button in, the whole cable assembly moved under the dash and as a result, the cable itself did not close the damper. I reached under the dash and pushed the entire cable back toward the seat so it was touching the back side of the hanger, then held the outer sheath on the cable so it couldn't move, then pushed the AC cable in. That took care of it. I think a simple recrimping would fix it if that's the problem.