I had a similar thing go wrong with that same harness except on the fuse block side. The alternator hadn’t been charging for who knows how long and the low battery light wasn’t coming on. Left me stranded half way home between Moab and Austin.Update
I did some research and found that the yellow wire on the 3 wire connector tells the battery light to go on or off. So I measured the voltage from that wire and it was .6 volts moving the wire around it jumped up to 13.6 volts and the battery light went out. So next step is to change that connector. By the way the way I was able to connect the meter to the yellow wire was I stuck a safety pin through the wire and connected a alligator clip to it. Hopes this helps someone in the future.
Happy Easter Mike