I assume that when you say "won't work," you mean that the fan won't come on. This could be a bad ground somewhere -- that's about all the climate control system has in common with the power windows. The windows, especially since they are on two separate fuses, usually don't go bad all four at once. A semi-bad ground will keep high-current loads (blower fan, window motors, etc.) from working but allow low-current loads (instruments, small lights) to still work. That makes the problem harder to diagnose. Anything else not working?

Mercedes has a number of ground points built into the car. One is behind the gauge cluster, there are a couple under the hood, etc. I think the electrical part of the FSM shows where they all are.

Bootsy, if you will go to the User CP and set up a signature line for yourself, you can add your car and model number so you don't have to repeat it on every post. You can also put in your location, if you wish.

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