This diagram and explanation is the best I've found. Scroll down one post. Get rid of that switch and wire it this way. Normally the light will come on as it starts and fades away as it generates. Having to switch it off means it's wired wrong. He shows how to jump the old regulator connector. If your connector is gone, just be sure the circuit paths are per diagram. If your truck still has the sensing wire, it is a funky looking wire/insulation and slightly larger in appearance. Sometimes it is looped back on itself to create a longer wire. The actual length is calculated for correct function. As he says, you don't have to have it but the light won't signal.
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