I have a 1998 Blazer and the other day my wife was driving and smelled antifreeze inside. I went and had the cooling system flushed and had them put back in the green stuff. Well the smell is gone but when she is driving, she notices the windsheild will get condisation by the defroster vents with all the knobs on off (fan, air conditioning, temp). What could cause this? I hope it's not the heater core, I'm really tired of working on this POS!

Sounds like a heater core leak. I've had similar symtoms with previous
cars, and it was always the core. You might check the hoses leading
to the core on the firewall for leaks at the entry point.