Quote:
Originally Posted by 767Jockey
Morris, this darned thing stayed on all the time.
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I think Morris confused you. A charging system that actually uses the idiot light does so by running current through the filament of the bulb to the voltage regulator. When it does this, it "excites" the VR to begin charging the system (assuming the alternator is working). The lead from the VR to the bulb is a ground circuit before the exciting takes place. Once the exciting takes place, it is a positive feed. So, when everything is running properly the bulb has a positive feed to both sides of it, so it doesn't light. BUT, if either side is noticeably "less positive" than the other, then the light will burn dimly. If either side is really negative, then the bulb will burn brightly. Sometimes the filament of the bulb does not have the proper resistance so you add a resistor in parallel. Now, here's your quiz in order to get an honorary Club Cobra EE degree: How do you measure the resistance of a bulb's filament when it always shows zero ohms when you measure it with your VOM?