My current 2002 Astro is the first vehicle I've had with rear heat/air, so I am not familiar with it at all.
BACKGROUND: I've had many times the common problem with a key vacuum hose breaking preventing the air to be directed through the vents front and lower vents, defaulting to the defrost (windshield) setting. That particular vacuum hose comes from the engine block to a "T". Strangely, after replacing it the last time, when I turned on rear heat, the air coming through the vents stopped and defaulted to the defrost flow into the windshield. When I would turn off the rear heat, the air started coming back through the vents. When making the repair, I noticed that another short vacuum hose coming from the "T" and going to another "T" was in bad shape--sticky rubbery and collapsed on itself. So I replaced that, and when I turned on the rear heat, the front vent stayed blowing air like its supposed to and so was air coming from the rear heat vents near the floor.
PROBLEM: My joy was short lived when there was very hot air coming from the front vents, and cold air blowing through the rear heat/floor vents. I did notice that coming from the "T" where two new hoses were replaced was another vacuum hose that heads down and "disappears" which is in that same horrible, partially collapsed shape as the one described above. Could this be the culprit?
BACKGROUND: I've had many times the common problem with a key vacuum hose breaking preventing the air to be directed through the vents front and lower vents, defaulting to the defrost (windshield) setting. That particular vacuum hose comes from the engine block to a "T". Strangely, after replacing it the last time, when I turned on rear heat, the air coming through the vents stopped and defaulted to the defrost flow into the windshield. When I would turn off the rear heat, the air started coming back through the vents. When making the repair, I noticed that another short vacuum hose coming from the "T" and going to another "T" was in bad shape--sticky rubbery and collapsed on itself. So I replaced that, and when I turned on the rear heat, the front vent stayed blowing air like its supposed to and so was air coming from the rear heat vents near the floor.
PROBLEM: My joy was short lived when there was very hot air coming from the front vents, and cold air blowing through the rear heat/floor vents. I did notice that coming from the "T" where two new hoses were replaced was another vacuum hose that heads down and "disappears" which is in that same horrible, partially collapsed shape as the one described above. Could this be the culprit?