Mode door adjustment

[1970pelle]

Installed the new heater core in the 86 C10 today.It has turn into a bigger job than just the core.Appears to have been leaking for sometime.The carpet pad was soaked and the floor on the passenger side has rusted.During clean up found about six very small holes.So pulled the seat, cleaned everything.Will start tomorrow on welding in repair panel.But I did finish up the core,new heater hoses,thermostat,flush.repaired overflow nipple on radiator.Fell off.But I screwed up the adjustment on the mode door.The arm fell off.Does anyone have the adjustment prosedure from the service manual??My has factory air.Vacuum operated mode doors.Thanks Ken