Replaced the blower with one from the junkyard. It's working now. It's not a definitive test because it has warmed up outside into the high 20's. My current explanation of what was happening is that the brushes in the motor were not making good contact in cold weather. I experimented with the old motor and my battery charger. Sometimes it would work when energized and sometimes it wouldn't.

Accessing the brushes in a 116 blower is not as easy as a 123. The motor is sealed. I may dicker around with it when I have some time. I think there is a thread here somewhere describing how to disassemble/reassemble a sealed motor.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13