[G.M.]

Almost all condensers will read good cold. You need to heat
them to 250 degrees and test them. When Skip rebuilds a
coil he asks the customer to send a few condensers so he
can hot test them. ALL stock new or used old Ford coils get
real weak when they get hot and come back to life when
they cool down. I have mounted small fans blowing cool air
on the coil which helped. Skips rebuilt coils run good when
hot. Skip puts a full 6 volts or higher on a coil to heat them
up until you can't pick them up and after his rebuild still work.
He has been rebuilding coils for well over 20 years and NEVER
charged to repair one that failed, except ones that left the
ignition switch on. If the points are open this is not a problem.
But if the points are closed the windings are like a resister and
get very hot. This melts varnish off the wire in the coil and shorts
the winding you will even have the potting material melt, xpand
and crack the case. Skips coils are insulated with an epoxy on
the wires and can take higher temps. Maybe installing a small
pilot light that is on when the ignition switch is on will save a lot
of coils. A small LED will work. You don't want much over 4.0 volts
to the coil on 6 or 12 volt systems or you will arc the points. G.M.