Is there a separate blower for the upper rear ducts?

According to the shop manual, air flow to the various locations of the auxiliary air is controlled by a mode switch. The shop manual lists procedures for troubleshooting that are too lengthy to even consider listing here. Testing hands on with proper equipment and reference material is needed.

Yes. The first under the dash, the second is located in the trunk area, on the passenger side, behind the cover. If you can't hear the blower motor back there, try the fuse, rear ac fuse is under dash, then you might try the module back near the blower. This was the issue when mine did the same thing. I got the module from salvage for $3.