about 5 years ago my climate control unit didn't change modes so i took a shot in the dark and replaced it with a rebuild unit and it worked. the other day i went to switch modes heard a big clunk and nothing. now it no longer switches modes, just fan speeds.

my question is how do i troubleshoot this? did the rebuild climate control unit fail? is it some other door or something stuck/broken?

Thanks

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1987 420 SEL | 87k miles
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