Today I solved my hvac problems that have been plaguing me and other mechanics for years.I have suffered from the dreaded no defrost and reverse air sucking sound with pop in other vents under load and no load.
the fix
Thoroughly cleaned entire engine after slight warm up with tire foam tub o towels and shop rags. Wiped clean and blew out with air. This leaft all vacuumed lines clean as a whistle. Plus my engine now looks awesome. From the bottom vacuum canister ball under front bumper I visually inspected all lines t joints and connectors throughout engine bay. Learning all the routes. After replacing any questionable fittings I moved to the sound check while running. Start engine and seek out any hissing sounds from vacuum lines. Slightly wiggle them to see if it promotes any sound escaping. More were found and fixed.

Next in a ventilated area, while engine was cool I sprayed the smallest amount of wd 40 while engine was on to the vacuum system lines. Anywhere I had leaks would cause a idle change. All lines in engine bay were true. Only one was left. The small line running into the firewall. Inside the dropped glove box you can see the vacuumed Mas connections. Made sure all was tight and checked to see if the visible hvac door and actuator in glove box would move while toggling through the hvac controller. Actuator moved and door opened. Next I continued to toggle through hvac setting listening for other actuators to move . I could hear the small whine of movement.

As seen on u tube and discussed on other threads I know took out my radio to have a look at the defrost actuator lever that is a thorn in the world side! It was gone. After some pondering I had the thought that Maybe it had backed out but was still attached the to the actuator arm. Sure enough I could feel it with my fingers dangling below. It was down and turned around. I toggled through the actuator settings until it raised enough to get my fingers on it and turn it around. Next I found the position on the hvac setting to best realign it with the connection and slipped into place. All was solved!!! All vents blew hard with no popping or sucking sounds in all settings. I about died . lastly I wondered why it had slipped of. I noticed that my aftermarket cd player from 2001 had a tone of wiring junk in the back cavity. That naturally fed and pushed the wires to the left side of the compartment right towards the actuator lever. I feel that while is spinning acomponied with leftward pressure it was forced out of its whole. I zip tied the mess and refocused it's slack away to the right side be fore reinstalling the stereo. I HOPE THIS HELPS SOMEONE!!JuiceMan2112 ​​​​​​​​​​​​​​