This problem started not to long after my wife was using the car and the coolant light came on she let some stupid sears people put dex cool in the engine. this car had never had dex cool used in it just standard coolant.
suddenly after the car has no heat ive check the heater core water flows easily in either direct i removed the vacuum controlled heater valve top piece with a pipe cutting tool so just the stud was left and placed the heater hose directly on it. I've changed the thermostat and refilled the system to capacity.
The outlet that is the hose that sends coolant to the heater core in take does not have any coolant coming out no more then a small trickle then nothing.I know this because i was able to remove the hose while running the engine hot and no big steam cloud what could be causing this.

307 Y ENGINE WITH COMP CONTROLLED Q JET ROCHESTER

 

not sure if this applies to your set up but this is what i found when i had no flow to the core of my truck

 

was that after a coolant change or anything that seems like it could be a winner
i let you know when the car comes back its still running like a champ im just trying to figure this out before it gets cold out

 

no nothing special i attribute that to 100,000 mile dexcool...i dont like it... i have had trouble with it...and i dont use it anymore

 

Stop driving it and get all that Dex Cool crap flashed out.

You cannot mix Dex Cool with the green stuff, it turns into a gel like stuff and, well yeah look at the pic above.

Complain to Sears!!! Don't know the extend of the damage, but it cannot be good