Chevy & GMC Vans

How do the rear heating and a/c systems that come stock with some of the Astros and Safari's work? Do they just extend the hot or cool air from the front unit and blow it to the back or do they include a second cooling unit and heater core?

Not sure how the A/C side of it works,but on my LT is does have a seperate heater core and blower for the rear heat.They tend to rust out the rear heater lines and I have already replace them with rubber hoses.

The rear AC has it's own evaporator. It's located behind the left rear trim panel. The air is ducted to the vents above the rear doors.