"philo" wrote in message
...
For those who may have missed my posts over the past year or so, my
background is industrial batteries and I have repaired literally thousands
of chargers whose output is anywhere from 80 to 350 amps.


When I was still new on the job , if there was a burned or tarnished
connection, I'd typically wire brush it down then sand it until everything
was smooth and shiny.


It did not take me more than a year to realize that was only a temporary
fix as the connection would always go bad again.


Once copper is heated it actually goes through a chemical change and
becomes copper oxide. If the burned portion is cleaned, the copper still
has a tarnished look to it.


If you cut a new copper wire and compare it to a cut, tarnished wire you
will see the difference.


That's why I said all must be replaced.


I agree. I worked with lots of industrial electrical equipment, lots of 480
volt 3 phase from a few amps to around 500 amps.

There were hundreds if not thousands of breakers and switch gear that was
inspected with an IR camera every year or two. If a connection shows
evidence of overheating, sometimes cleaning and tightning would solve the
problem, but often it would show back up on the next scan , usually about a
year later.

Cutting back and changing seemed to be the long term solution.