Generator light - Impala Tech
Electrical & Wiring Troubleshooting electrical problems

 
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post #1 of 4 (permalink) Old 11-03-2013, 02:19 PM Thread Starter
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Join Date: Nov 2011
Location: Texas
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Generator light

A few months back I replaced the generator on my 62 impala with a three wire alternator. Since I've made this change, my dummy light hasn't come on when I first turned the key. I figured the bulb was out and because the alternator was new, I didn't bother looking at it until this morning. What would be causing lack of the light?

I've read a bunch of treads on this forum and come to the conclusion that I have it wired correctly and the Wheatstone bridge should be detecting the current even though its not factory.
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post #2 of 4 (permalink) Old 11-03-2013, 05:42 PM
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You are mostly correct. The bulb may not be wired into the circuit at all, or there is a resister in the line somewhere with more OHMs than the circuit requires to operate correctly. I'm betting on it is not wired correctly (as the factory intended with a 10DN alternator).

To test this theory you need only disconnect the red wire and crank up the car. If it runs with the red wire disconnected then "gen" light should be on (because I guarantee it isn't charging).

The light circuit in the alternator used a diode in the line added to the resistance of the bulb to determine if the light would light on a discharge and not allow current to flow back through the light to energize the cars ignition once the key was turned off. this is different than the way a generator light was wired which didn't rely upon electromagnets to energize the charging field (Generators use permanent magnets to create DC current directly; while alternators use electromagnets to create AC current that is later rectified to become DC current).

Big Dave
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post #3 of 4 (permalink) Old 11-03-2013, 05:57 PM Thread Starter
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How did I know that the transition wouldn't be that easy?

So the next question is, how do I correct it to make it work properly again?
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post #4 of 4 (permalink) Old 11-03-2013, 06:14 PM
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There are a number of how too's on the Web as this is a fairly common upgrade.

I would look at a 64 or so wiring diagram and just copy the factory circuit. I would leave your wiring as is, and add a separate circuit from the alternator blue wire to the dash warning light that you can hide in the factory wiring rather than try and splice into the factory wiring (which is old and brittle).

Big Dave
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