Mine just started making a cracking noise like you describe this morning when the temp dropped below freezing. It drove me nuts, thought it could be the speaker somehow, but I took out the glove box and found it's the actuator/motor that controls the climate control. That's actually the reason I came across your post, I'm checking to see if others solved the issue since I dont want to replace it only to find out it's not the true issue.
Sounds like it's the case though, theres several of these behind the glove box on the side where the cabin air filter is. Follow the noise and unplug the culprit, if it stops you likely found the one that needs replaced.
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