Well, no heater box so far. Did manage to break my AVS some more.
When I took it apart I blew compressed air into the check valve in the lid that lets in air to some port of some kind, making the ball inside jump to the top of the spring. I realized I wouldn't be able to get it back to where it belonged without damaging the ball seat, so I took it out and apart.
Does anyone know where to get hold of a new one? And the plug that goes over the adjustment screw.
These are the parts:
View attachment 1715033860
And this is where they go:
View attachment 1715033863