I only have air comming from the defrost. So I replaced the Vacuum pump, still nothing. Lines behind the glovebox seem fine and lines going to resevoir and from pump seem okay. lines to hubs seem fine. my Auto 4x4 has never worked since I bought the truck either, and I know my one hub is not in great shape which explains the no auto 4x4 BUT vents were all working fine before, 4x4 never did. Any ideas? I've read a little about some sort of solenoid broken somewhere that might be the cause of it? I'd like to exhuast every option myself before I take it to the dealer to get fixed. Kinda cold out here and sucks to have no heat on my feet!!!