is it possible that the vent hose are disconected?
nothing but the floor pan
ignition on - engine off - floor the gas pedal 3 times. That's it!
Heater core is leaking. Air Conditioner drain hose is plugged.
On the back of the intake manifold are some vacuum hoses. Check and be sure all are attached . If they are good the you probably have a blend door problem.
Check under the hood for a broken or disconnected vacuum line.
I had the same problem with my caprice a few weeks back. The water shouldn't be dripping from the back, it should be dripping on the rear passenger side floor board. That is caused by the heater core being bad, which is causing the water to seek through the carpet and drip out the back floor board.
the heat blows out the defrost when it should blow out floor vents only
heater core....
The blower might need replacing. Normal cause is a failed blower resistor, caused by a blower fan that is failing.The resistor and fan are located above the passenger side floor behind the glove box.
Check upstairs heating unit.
In my 87 I had the same problems and I came to find out that my tranny was going out thta. Is what the problem sounds like to me.
Volume of the room.