it is the vacuum actuator for the defrost, on the passenger side, the one on the driver's side is the heater...
Good luck with the project
74 wag, 349Kmiles on original ticker/trany, except for the rust. Will it make it to the next get together without a rebuilt? Status: needs a new body.
85 Gwag, 226 Kmiles. $250 FSJ test lab since 02, that refuses to give up but still leaks.
See Ouray 2013
, Engine bits
and Fuel and brake lines
, and Body work