Originally Posted by BillBoost37
Not sure I agree, maybe I'm not fully understanding. However it'* a whatever we can do to help situation.
When you say blocked, do you mean airbox internally or inside the piping of the core itself? I am thinking you mean the latter.
How can we have him test or check that w/o pulling the heater core not knowing if it will fix the problem?
95 and 98 can you blocl off the passenger side vents partially and see if you get the warm air out the driver side when the passenger is blocked? I assume you should get more flow and warm air.
I am thinking the latter. That internally, the coolant passages of the heater core become blocked in such a way that only one part of the core warms up. then when air passes through the core it is only partially heated. (Now here is the hard to believe part) - that the air remains largely stratified as a separate layer of hot and cold air as it moves through the ductwork and because of the arrangement of the outlets, the hot air exits on the passenger side. That'* why I thought the flow would have to be laminar, especially after it passes through the core. If it was turbulent and mixed, the temperature would be more uniform as it exited the ductwork.
I admit, this is just a guess. But it might not be that far-fetched. Consider the function of the screen in the throttle body. Not unlike the air passages in the heater core, its purpose is to produce laminar flow for the MAF sensor.
If this guess turns out to be correct, the only real fix will be to replace the heater core. [edit: EXCEPT...
Bill W may be right about a portion of the ductwork undone. This might produce a similar effect, allowing cold air to be sucked in to the air stream after the heater core. In that case, the core might be OK, and you would still have the problem. What we need is a warm junkyard not under a foot of snow :( where we can study the actual system and figure out what is happening. The diagrams in the FSM and pix of the exterior are helpful but don't provide the internal pathways we need to examine.]