Thanks again to all who responded to my dilemma. Turns out that the newest guy in the shop rebuilt my alternator, and did not put the terminals in the same places as the OEM unit. I would recommend that any of you who choose to have your alternators rebuilt at a local shop take a digital photo first and remind them that you would like to get it back with the terminals in exactly the same configuration.
When I described the problem on the phone(more eloquently than I would have been able to without the informed responses of this Board) the folks at the shop invited me to drive the car (only 3 miles away) to their place at 5 PM. An amiable British fellow, familiar with vintage Volvos quickly determined the problem and wired the alternator correctly.
The Brit volunteered his pleasure at seeing such a good specimen of a 240. He said that the roads in England are heavily salted due to frequent freezing, and that most cars are eventually destroyed by corrosion.

Phil Loizeaux in North San Diego County