This is very true on AC solenoids. A fully inserted core closes the magnetic circuit and greatly decreases the reluctance ( which increases the inductive impedance, X(L)) of the coil, dropping it's current draw significantly.
However with DC, it won't work this way. Unless there is some sort of switch in there to include another portion of coil winding when the core fully inserts.
My strong suspicion is someone has changed the manufacturing process of these parts. It seems the big thing these days...some MBA/Accountant type lands a Corporate job, and in his excitement to demonstrate his worth by cutting costs, he makes changes that the rest of us have to live with.
I've been around these "Wall Street" types. They have different skill sets and motivators.
It wouldn't surprise me at all to see them instruct the factory to wind the coils with aluminum wire or some low grade copper to save a buck .
I personally had so many problems with after-market glow plug relays that I ended up using the same industrial White-Rodgers contactor design that Wes is kitting for manual glow plug conversions.
We used to think newer meant better.
It's not just us. Imagine all the businessmen who paid big bucks for the latest technology where others come into your machine and change things.
Latest Windows Update Has Borked VPN Use on All Versions -- article related to The Main Page and Security.
soylentnews.org
Boeing hasn't been having much luck keeping their planes from falling apart mid-air either.
All I can do is come to the conclusion that modern business types and I just don't think alike. We have different goals. Once these guys get control of the boardroom, company's over.