It is also possible that leaves and dirt have accumulated in the fresh air intake to the blower. That would cause the blower to slow, make bad noises, and drag down the system voltage so the lights would be dim. There is supposed to be a screen protecting the blower but maybe it is loose or missing. As was said, the blower is hard to get to but can be cleaned out and then might work normally.

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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