1. Is there heat available when the temp slider at high? Check the heater system as others have indicated.

2. When the Defrost button is in and all others out, is there air only at the windshield vents?

Since the blower was replaced, and if number 2 has no or little air at the vents, you will have to trace a vacuum problen in the vent controls.

First place I'd look is under the hood, off the top of the intake manifold, the small hose off the check valve that leads through the firewall. Pull it off and apply vacuum. There will be a point where it will not allow air to flow freely.

There should also be vacuum off the manifold through the check valve.The air laeak is so small if the hose is disconneced it will not set any codes or affect engine running.

Duane