'95 suburban AC in rear seats

My '95 Suburban has very good A/C for the front seats. However, when you turn the A/C portion on for the rear seats, the air comes out warm.
I checked the owner's manual to make sure that the truck was supposed to
create cold air in the back, and I do have the model that does both A/C and Heat in the rear of the truck.
Any ideas on what the cause of this might be?

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.