A poor connection has resistance, resistance under current makes heat, and heat leaves marks. Those marks mean the connection needs investigating, not tightening.
Discoloration is evidence of damage that has already happened. The metal, the plating and the insulation around it may all be compromised, and none of that is fixed by turning the bolt.
Think about what the discoloration is. It is the record of a connection that was running hot -- possibly for a long time. The heat was produced at the joint and everything at the joint experienced it: the lug, the bus, the bolt, the conductor and the insulation. Tightening addresses the looseness and none of the consequences.
Check yourself: A discoloured lug is loose. You torque it correctly. Is it fixed?
Answer: No. Tightening a damaged connection does not automatically restore it to serviceable condition.
The discoloration means damage has already occurred. Correct torque on damaged metal is a correct value applied to a part that may no longer be serviceable.
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Written from the owner's poster for this lesson. Nothing added beyond what the poster states.
Written for Texas apprentices as free study material. The Texas apprentice licence is an application, not an exam (Occupations Code 1305.161), and nothing here counts as apprenticeship hours or continuing-education credit. VoltMark is not affiliated with, endorsed by, or sponsored by NFPA, PSI, TDLR, or any state or local licensing authority. Always follow your employer's safety programme and your supervising electrician.
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