A/C blowing out bottom
#3
theres a vacuum line in the engine compartment. maybe its damaged or unhooked. should be on the passenger side and go into a wire harness. that line feeds into the heater controls under the dash. from there the lines go to the control valves.
#5
check the vacuum line under the hood. it hooks up to the passenger side of the intake manifold and should go into the passenger compartment wiring harness. do you hear a sucking noise inside the car when engine is running?
#9
does it go into a wiring harness or into the firewall? should go to the passenger side of the intake manifold. have a look at this 1998 HVAC hoses/lines, how to route and connect? - LS1TECH
#10
There is a small t-fitting between the a/c evaporator unit and the pcm at the firewall. See if it is broken or if any of the three small hoses are disconnected. The photo is for a 95, but the 98 fitting is the same and in the same location.
http://shbox.com/1/vac_check_valve.jpg
http://shbox.com/1/vac_check_valve.jpg