woscarr, Did you ever find the fix for this? I have exact same issue on my wifes 99 Venture. I have started tearing apart the center console and glove box as I believe like you that there is something preventing air flow across the heater core itself. I noticed on Saturday when I was under the dash that alot less air comes out the floor or panel or defrost when you change the temp from cold to hot. Any insights would be appreciated.
