No air across heater core

I hear loud air blowing yet get no air through any vent. I have air in front of the heater coil and the evaporator but none going across the coils. I checked vacuum to all contols. All ok. I cut access holes to see the vents operate. The electric door to regulate the down wind side of the coils works fine (modulates heat/cool). Defrost vent opens and closes. I even drilled an access hole on the engine side of the duct, just after the blower and air does blow out. Yet on the inside of the car there is no flow anywhere. . My question is, Why does the air stop flowing?

Is there a vent between the blower and the coils, like a primary vent which may allows no air to the coils? Where approximately is it located where I could at least open it and get airflow? Or are the vents only after the coils? I think I see a screen covering the evaporator. Is there also one on the heater core which may be blocked? Seems unlikely to stop ALL airflow.

Sorry if this sounds confusing but I am baffled as to why air is being pushed, all vents do appear by sight and sound to be operating, including the electric motor yet I can get no flow south of the coil.

Here is a clip from a similar situation.

> both driver and passenger valves are working(i could hear the motors and feel the >valves moving), replaced the cabin air filter. Looking at the diagrams in the repair >manual(WPB-3), i believe there is a blockage at the heater core somehow. What could >this blockage be?

What year is the car ? I've seen some older ones where the evaporator gets totally clogged.

Thanks for taking the time to reply.
My car is a 1986.
I thought the same kinda (evaporator crudded up) but the heater core also? The air flow is so restricted there is only like maybe 3 percent getting through the vents.

Could be, I suppose but it just seems that if it were so restricted that it must be a vent door. But I wonder if there is a door BEFORE the evap/heater core.

Someone also said there is a prescreen on the evap to keep stuff out. But to restrict it THAT much???

Please reply with anything you can think of.

The wind blows through the evap first then goes to the heater core there is no door. Go under the hood take the blower motor out. Look down inside the metal ductwork toward the center of the car thats where the evap is. It probably covered with crud.

Thank you so much for the help. Im having a rough time with the blower motor because a bracket on the engine is in the wat, I'll have to do it on the weekend. Plus I have to get the squirrel cage off from the inside I think cause there isn't much room to tip it up and out. But that does answer my question about the airflow. It's hard to picture it under the dash (upsidedown too). But at least I know there's no door BEFORE the evaporator.
Thanx a bunch man!

You quoted my post in your initial posting. I corrected the problem i was having by replacing the thermostat. This may not help in your situation, but i figured i would mention it since you were looking at my post as a similar situation. Also, a new thermostat is inexpensive and who knows, maybe it will help. I certainly didn' think it could possibly be the cause of my problems, but it was.