can't seem to figure out why the airflow coming out of the vents for a/c is so weak. have changed blower motors a couple of times, so not convinced it's that. am more inclined to think that the vacuum "doors" aren't opening enough due to being old, or maybe not enough vacuum to open them up... got about 17" at the plenum. defrost mode has the same effect - weak airflow.

 

Since the air will divert to the various outlets and ducts, I would suspect that either the core case is not sealed, the blower housing is not sealed, the AC evaporator core case is not sealed, the evaporator core itself is clogged with debris, or the fan motor/blower wheel has a problem.

If air flow seems normal at some temperature setting other than full cold, the evaporator core may be plugged with debris. If flow is the same whether the temperature control is full cold, middle range, or full hot, the other problems might be worth investigating first.

 

temp doesn't seem to change anything - airflow seems to be the same. a few years ago i replaced the heater core, recently when i did my rebuild i opened the evap case somewhat, don't remember being able to open it all the way as i recall something was in the way of that, but anyways i felt all around the blower housing core housing and evap housing and felt no leaks. power is equal to batt voltage at the blower motor connector, resistors are intact, all fan speeds work...

this might get a better response in "cooling" but maybe there should be a new forum added for heat/ac discussions...

 

I agree with Vadar, sounds like the heater core case may be leaking. Do you hear any air leaking around there. Also do you hear any sucking behind the Heat/AC unit?

 

Have you checked the blower wheel for debris?