What is this doo-dad (circled in red) on the back of my alternator? There is a brown wire from it to the B+ terminal. There is not a device like this on the spare alternator I took from my old '79.
Does the device in question have anything to do with energizing the field so that charging can occur?
I inquire because something has been puzzling me for a while. I bought the car in Oregon in 2001 and the previous owner informed me that the alternator warning light didn't work. All it meant to me at the time was that I should replace the bulb. I have since learned, in this very forum, that the warning lamp must be functioning in order for the alternator to start charging the battery. I drove from Oregon to Kansas City over the course of four days with the warning light not functioning. I drove mainly during daylight hours but I used the headlights a few times the longest being for about three hours on the last night of the trip. I continued to drive the car occasionally for a couple of weeks before I looked for the cause of the problem. It turned out that the thinner red wire from the warning light to the alternator was broken. I spliced it and the light worked. I have not had any battery/alternator problems before or since.
It seems to me that, even without using the headlights, if the alternator was not charging the battery, the car should have shut down somewhere in Idaho or before. Do I just have the worlds most powerful car battery? I can't see any other sign of creative wiring to the alternator. Being an electrical dumbshit, I am at a loss for an explanation. Unless the warning light 'on' condition is not true of all 240 alternators. Enlighten me, please.
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'80 DL 2 dr