That box is your HVAC unit that houses the heater-core and evaporator. Two companies made the HVAC units for your van. The front system Valeo and the rear system Denso.

I know how to work on the rear unit rather well. I've tore it down and put it all back together a few times already. The front unit is more complicated and requires a technical manual to dig into it. Hanes and Chiltons covers this to some detail. Just be glad you do not have the pre-1998 HVAC unit for this van. Those are a real pain to tear into.

These images are general to either the older or newer HVAC units.





Pre-1998 vacuum arrangement

 

So what would I need to look at to firgure out why the back vents are not blowing?

 

Thanks for the responses, I have found the second fan motor and it was a bad relay!