I've a 2005 Mercury Sable.
We discovered when the heater and fan is running, there was a rattle and smoke!
We discovered that one of the three caps(?) on the A/C compressor had come loose, and that's where the smoking was coming from. It finally came off, and the inside is melted.
Then, after that one came off, a 2nd one popped right off!

What's happening? Why in the world would 2 of these caps come off on their own like that? And what caused them to melt inside? Is there some moving part they're covering?

Background:
This started last night after we took a sharp curve to the left too fast. All of a sudden that's when the noise and smell started. Did that cause it to shift? Is it migrating off it's bolts? Is it about to come loose and crash around?

Additional note:
I have no idea if this is related, if it's bad or nothing... I may be paranoid, but it seems to me that the spinning pulley part on the compressor is wobbling just a teeny bit against the pink bushing or gasket (?) that's between the pulley and the three capped bolts. However, those three bolt ends and the plate at the end don't appear to move at all.

Anyway, thanks for any suggestions or advice!