[SOLVED] What is this and how does it work?

[sundaydriver]

Can't figure out what this does. The little piston doesn't seem to extend far enough to touch the accelerator lever, so not sure what it does.
Also, because I don't know what it's called/does, I don't know what to Google!
'83 VH Blue 3.2 202.

 

[gtrboyy]

Air con idle solenoid