I am new here, signing up to figure out what I did wrong in repairing the heating on my 1996 Suburban C1500. I am scratching my head, please help.

My fan blower was making a nasty screeching noise in cold weather, plus the medium 1 fan speed setting was not working. I took out the blower motor, lubricated it, cleaned out the area around the blower motor (pretty clean really for a 16 year old car). Blower works fine now, no noise. Then I changed the A/C & heater fan control switch behind the dash, now all fan speed settings work. So far so good.

Now with everything put back in place the air flow through any of the vents is not a fraction of what is was before! I checked the air-flow direction actuator: it seems to work, a bit comes out of the defroster when directed there, and also from the other outlets. The blend door also seems to work: I can adjust the temperature of the bit of air air coming out. I took off the cover underneath the heater core (not too hard if done with a very thin 1/4 inch ratchet), and the inside was super clean. The flap door for inside circulation (close to the blower motor) seems to be working too. So what the hell could possibly be restricting the air flow? Is there another flap door I don't know of? Is there a flap door in the air flow direction actuator that could be stuck?

I ordered a replacement for the A/C, heater, blender control console, since that seems to fail often, but I'd rather not put in a new $ 140 part if that is not the culprit.

Any suggestions from people who have more experience with this than I do -- this is the first time I ever did anything with the heating system.