I finally got the plug off. Still don't understand how it operates but at least it's off. The glow plug itself, BTW, was trivially easy to remove with a 12mm deep socket and a 3/8 inch ratchet. I sprayed it with Aerokroil while I figured out the connector. One or two clicks of the ratchet and it was then loose enough to remove with fingers. Remarkably clean, too, a shame it's deader than a doornail (whatever that is).

The last step, after installing the new glow plug, is to repair the #4 connector, which I broke while "practicing" for #5. Always something!

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970