Cars - Bad rectifier or component in alternator drains battery.

A 1988 Ford Escort with 1.9 L inline 4 has a 6 amp drain out of the
battery when the ignition is off. The initial symptom was a weak
battery unable to start car. Car started when jumped, but battery
didn't appear to charge. In circuit voltage test showed 6V, and
battery assumed bad. Battery taken to PEP Boys (Local parts dealer)
who tested battery and said it was fine. Of interest was that out of
circuit the battery voltage was 10V, which was a hint of heavy current
draw. Back to the car went the battery, and 6 amps were seen coming
out of the battery with ignition off and all lights off in car,
including the under hood courtesy light (one of the nicest touches of
the Escort). Disconnecting alternator at both connectors ended the 6
amp draw, with car pulling only 20 mA after alternator disconnected. A
new alternator was installed and the 6 amp draw is gone.

The counter guy at Pep Boys confirmed that alternator failure manifest
as heavy current flow when the engine is off is a common failure mode
for an alternator. Apparently the rectifier diodes in the alternator
short out and allow reverse current to flow and drain the battery.
Modern cars have the voltage regulator integral with the alternator.
It used to be you could buy service kits with new diodes and replace
the failed parts.

Given that I have had 18 years of service and over 160000 miles it
looks like I got good service out of the part.

I'm posting this so that others who try to fix their cars with a VOM
and Google can find a hint.