The wire in the middle is the level sensor. The wires going to the solenoid in the back right power the autofill solenoid.

Which, iirc, is not connected on your machine.

Thanks for posting the pic...a real memory refresher as I look at the autofill probe directly in the center of the boiler and the autofill solenoid in the upper right. Man oh man it was a different machine that I removed the autofill system...the Astoria has the autofill alright! All these years of relying on my memory to find it to be increasingly unreliable...guess it is time to start taking better notes!

That valve on the left is the vac valve indeed and Astoria uses a strange valve which has no stem on top. It has a teflon part inside that is shaped like an old fashioned spinning top, or a turnip, and the small end goes into the valve seat. It can get out of alignment and that is why the whack stops the leak. If you take off the top cap you can see turnip and see if it needs cleaning. Also one can change to the standard brass weighted one with the stem and o ring if this one keeps acting up. They seem a little less prone to sticking or getting out of alignment.

An easy way to disable the autofill is to remove the Gicar controller - on mine, at least, it is socketed and held in place with a screw; remove the screw, wiggle it out, no more autofill. And no dangly wires or electronics being powered. The clearance is pretty tight between the controller and the sight glass pipes, but it'll make it.