Rochester Quadrajet 4v Solenoid

[Classics Fan]

I have a 1971 Jimmy with original rebuilt 350 and A/C. Questions about the carburetor solenoid: first, is this an idle stop to prevent dieseling, or an idle increase for the A/C to prevent low idle stall?

When I start the engine, the solenoid plunger extends (sometimes, not every time) for a few moments then retracts. This action seems to happen irregardless of whether the A/C is in the or off position. The A/C belt was removed by the PO and I have never replaced it so I’m not certain whether the air works or not.

Where does the solenoid get its power, and what possible causes are there for it to only work momentarily, intermittently? I have the idle speed set using the designated screw. If the solenoid is for idle stop, then why is there also an idle speed screw?? Thanks in advance for any insight to help clear up my confusion.
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