I too want to know what that flat rectangular module with a single wire is on the back of my alternator. I think we both know we have an external regulator attached to the firewall area. I just burned out two alternators in two weeks. I had a new rebuilt bosch alternator installed by a professional after installing a fast glow plug set up. I'd go back to him, but after many years, he just closed up shop and moved away. I replace that one myself with another bosch rebuilt, and I'm very sure I reattached all wires the same way. But, of course, maybe I didn't, so I'm in the same boat as the original poster. After the new alternator is fired up, it only takes a couple of restarts before the alternator dash light goes out, and I assume the alternator is again burned out. I had the previous one bench checked to find out for certain. Also, is the alternator supposed to be mounted with a bushing? Mine is not.