Hi
I have a 1975 w115 MB 240D that has a defrost issue.

The defrost doesn't work. The problem is that it sometimes turns on, but it is unlikely that it works.

I've heard that the defrost is activated with a vacuum. Is there anyway I can bypass the vacuum to test the unit? Where are the connections for the vacuum and the connections for the power located?

Thanks for any help.

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1975 W115 240D