coil observation- meaning, if any?

[Russell]

I just replaced my valve cover gasket and spark plugs. I took the opportunity to test my coils 3 ways, night/dark observation, spark gap device and ohm redings. The spark gaps and ohm readings all read the same for each coil so I think my coils are still working OK after 203K. That said, they may be a little weak?

However my obeservation of the coils in the dark revealed a very soft pulsing glow around each coil. Only observable after your eyes adjusted to the dark. Very hard to see. Does this indicate anything?

[Bill R.]

Read up on corona discharge. Applies to coils, plugs and wires... The discolored porcelain base on a spark plug where it meets the metal is usually the result of corona discharge. I've never noticed any harm to any engine from it though.