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Old 08-04-2012, 09:52 AM
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Bypassing external voltage regulator

If you had an old car without a wiring diagram, 50 Caddy or whatever with an externally mounted voltage regulator and you wanted to install a modern 12 volt alternator (say the generic AC Delco with internal regulator installed on 70 GM cars) how would you go about bypassing the external regulator if you didn't have a wiring diagram?

My 68 Ford Fairlane has an alternator but an external regulator. It has a four wire connector going to the regulator.

If the car has a generator, it should not have a rectifier (since it's already producing DC voltage) built into the regualtor. If it has an alternator, the regulator should have a rectifier built into it.

I'm assuming the first thing is to test the each wire with the car running and see what happens.

Say if this is on my 68 Ford Fairlane:

1) If one wire should give some crazy reading that should indicate it's AC current (input).
2) If one wire gives a steady voltage reading, that wire should be the (DC output). This wire should goto either the fusebox or back to the battery.
3) One wire probably goes to the battery light in the gauge cluster.
4) I have no idea what the other wire goes to. Ground perhaps?

I actually have a wiring diagram for this vehicle but that's not really the one in question.

I would think if you installed a 12 volt alternator w/internal regulator, the best way to wire it up would be to run a wire off the back of the alternator directly to the battery or post on the starter or starter solenoid.

Then disconnect all wires at the regulator. Hook the battery back up then start the car (if it starts) and see what happens. See if the voltage at the battery increases and what circuits work.

Maybe tie the DC output wire coming off the regulator to the alternator?

Where would you go from there?

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Old 08-04-2012, 12:17 PM
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If you use a GM 1-wire, just connect the red Bat wire from the alternator to the battery (or horn relay as in the case of a Corvette) and make sure the case is grounded. You can also run a ground wire to the case as back-up.

Just disconnect the other plug/wires (the Field and Lighting Boost) at the alternator, and let it hang or cut the plug off the wires and tuck them back into the loom.

On a GM the plug on the voltage regulator can remain or you can unplug it. In the case of a Corvette (the basis of my experience), there is a "condensor" attached at the voltage regulator that you would disconnect if you pull this plug off the regulator. But the condensor is only for radio noise suppression and doesn't affect anything else and you may not have it.
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Old 08-04-2012, 07:26 PM
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Converting From a 6 to 12 Volt Electrical System
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