8000 charge light

FordTractorMan · Mar 31, 2015

I already admitted to being pretty stupid about wiring, but I dug out the shop manual and looked at the diagrams - not sure I'm much smarter for the effort. Near as I can tell, things are hooked up right. I still don't know why the bulb won't light up. I replaced the single wire socket with the original, and again, I have juice from the ignition in the center of the socket and it'll light up my tester. I checked the yellow wire coming from the alt and it barely lit up the tester. I think the book said there should be 2 volts coming from the alt to the bulb? I may need to go back and look. This is all w/engine off, switch on. Any further thoughts? This enough info to go on?

Sean in PA · Apr 1, 2015

What's the voltage on the second wire when the key is on and the engine's not running? According to Ohm's law, E=IxR where E is the energy potential in volts, I is the current in amps and R is the resistance in ohms. So in order for it to light up there has to be a difference in voltage across the bulb, and a path for the current to flow. If there's no voltage when the key is off and there is voltage when the key is on, and if the second wire has exactly the same voltage as the first, then it's not going to light, and would indicate that the circuit is not complete. Where does the second wire go?

FordTractorMan · Apr 1, 2015

Thanks, Sean. The yellow (w/black stripe) wire goes from the alt to the side of the bulb, and the dark green wire goes from the ign switch and contacts the center of the bulb. I need to invest in a multimeter so I can check voltage. Another interesting detail I neglected to mention: when I turn the switch on, and touch my tester to the side of the bulb, both the tester and the bulb light up weakly. Bad ground a possibility?

JMOR · Apr 1, 2015

(quoted from post at 08:53:58 04/01/15) Thanks, Sean. The yellow (w/black stripe) wire goes from the alt to the side of the bulb, and the dark green wire goes from the ign switch and contacts the center of the bulb. I need to invest in a multimeter so I can check voltage. Another interesting detail I neglected to mention: when I turn the switch on, and touch my tester to the side of the bulb, both the tester and the bulb light up weakly. Bad ground a possibility?

ellow wire from alt or alt itself will be your problem.

8000 charge light

FordTractorMan

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Sean in PA

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FordTractorMan

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JMOR

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