To have power anywhere in the car with the engine actually running (as opposed to "switch in position #2 RUN") would take a dedicated relay working off of the alternator light. That way, once the engine is actually running and the alternator producing current, the alternator light goes out, the relay trips off, and your accessory pump gets power.

Jeremy

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"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