Thread: Overheat?

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It does look like heat discoloration. Did you take a temp reading?

As for the cause, most likely a loose connection.

Previous overheating - I wouldn't venture a guess as to what from, clients remember the strangest stuff - often not what you meant or said. You say it MAY be from a poor connection - they hear it IS from a poor connection.

Grounding is wrong, though not unusual.

The discoloring may be from the original manufacture, or it just may be old, excess 'grease' that often comes on breaker contacts. Or, there may have been a breaker go bad in that spot. I don't really see any cause for concern.

While extreme heat will affect the 'spring temper' of any metal, the way panels are constructed make that a concern only for the breaker part of the connection, and has no effect on the busses.

As for the air conditioning disconnect, I do not see a problem with what was done. It's an older disconnect, which likely had no ground terminals. I'm glad the guy bonded the enclosure.
Two wires under the lug? While I don't like it, it may just possibly be legal; many such lugs are listed for as many as 3 ground wires under each screw.