The drop in voltage is severe, sometimes to the point where the engine will die. This symptom started abruptly too. Seems like -10 degrees F could have triggered it....
I am thinking the regulator or alternator is the culprit. It tested OK on the bench, but the problem is intermittent. I despise intermittant problems. I wish the lousy part would just fail so I can figure it out.
How long do alternators last these days? Mine'* at 187k, that seems like a stretch but I would be disappointed to drop $130 to find out it'* not the problem.