No defrost/vent selection '92 rmw blend door actuator??

my '92 roadmaster only blows out of the mid level vents and not very hard; if you put your hand around the defrost vent and floor vent you can feel a very small amount of air moving. this is the same regardless of vent selection. When my hvac system was working properly last winter i used to hear like a vacuum leak from under the dash when i shut the car off. now i dont hear anything.

i took the front of the dash apart and started poking around underneath it. i followed some of the vacuum lines from the vacuum manifold to diaphrams under the dash to see if one had come off. no luck. ive done a bit of research and im starting to think my problem could be the blend door actuator... wheres the blend door actuator located under the dash?? i need defrost! and more heat!! or is there anything else i should check?

Did you ever figure this out? I have an issue it seems with my 92 OCC, I can switch vents just fine but when I switch to bi-level, I get almost no air out of the floor vents, but plenty out of the dash vents, also there is no vacuum hiss when switching to bi-level.

I had an issue on a 91 Cruiser similar to this. In my case, there was a vacuum line that goes to the engine which had a hole in it. Replaced the tubing and it fixed it. Easy line to check, runs (if I recall correctly) along the inside of the passenger valve cover to the front of the throttle body.

Worth a check!

still havnt figured it out. still have heat, just no selection. vacuum feed line off the TB seems fine. i have the full service manual for the car, theres alot of vacuum lines in the dash. no time to check it out though. ive pretty much parked it for the winter. if i recall the vacuum feed for the havc runs with the main wiring harness into the passenger side firewall. then theres a vacuum manifold which distributes the vacuum to various actuators and sh*t.

My only issue is the floor vents don't seem to open. So that narrows it down but it's hard to troubleshoot when it's 0 outside. At least I have heat and defrost!

fixed. pulled the dash apart started tracing vacuum lines. first line i tested for vacuum was the feed line and got nothing. ran a separate line from the throttle body to the inside of the dash because i didnt feel like tracing the old one through wiring harness loom in the cold. its good to have defrost again!