I have an idiot light of sorts on my '49 with a 350 in it. It has a '93 alternator which only has two wires. One is the big red one held on by a nut on the back, and a brown wire which goes to the ignition 'on' terminal. In series of this wire, I added a simple dash light which hangs under the dash. This is the original design of '93 alternators.
It has a dual purpose.
#1. It energizes the the alternator. The resistance caused by the light bulb is what triggers the alternator to energize. Once the engine starts, the light goes out.
#2. If the alternator stops working while the engine is running, the light comes on to tell me that I am an idiot. (Why else would it be called an idiot light?
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