Yes it will if the A/C compressor is not running and the control is set to vent, it will heat the air that is being drawn into the vehicle, but if it is coming out of there all of the time then you have something wrong with the control systems.
If your Electronic Climate Control System is the same as on my '94 Fleetwood, no. The heat will only come out of the floor vents. Cadillac did away with the bi-level setting many years ago. HTH. -Jim
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