Did you check the 30 amp metallic strip fuse located near the fuse box? They have a tendency to crack. It's located toward the passenger side of the fuse box. Small rectangular box with a lid. Metallic link is held in place by phillips screws.

Also, There are three wires going to your blower ass'y. Battery positive, ground and a signal from the control to the speed regulator. You should see around 6-8 volts on that one wire if the pushbutton unit is working.

Another possibility is the ignition switch. Try gently moving the key a little and see if the fan comes on.