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12v Alternator converstion and some misc questions
#789355 Sun Oct 16 2011 11:16 PM
Joined: Apr 2011
Posts: 96
akguy34 Offline OP
Wrench Fetcher
Okay I have a few questions I have come up with while trying to figure out the 6v-12v conversation on my '46 Chevy 2 ton.

#1 I'm installing a 12v alternator, the one I have is a single wire internal regulated model. I was under the impression all I needed was to run a single wire from the alternator to the pos battery terminal. While reading the conversion tips it stated a DA wire is added and the wire goes to the ignition switch. Which would I do?

#2 in the wiring diagram I see a polarity reversing switch in-between the coil and distributor. I didnít see anything else in-between the coil and distributor, Is this and internal part? Do I need one?

#3 when I replace the 6v coil with the 12v coil I plan on getting and internal resistor model, do I need any type of voltage reducer for the distributor? Or will this act as one? Do I replace something in the distributor to convert it to 12v?

Any help is appreciated.

Re: 12v Alternator converstion and some misc questions
akguy34 #789390 Mon Oct 17 2011 01:22 AM
Joined: Nov 2005
Posts: 5,682
3B Offline
Master Gabster
Hy akguy, I'll answer your questions in the same way you asked them.
#1 If your alternator is a true one wire alternator, then you should hook the wire from the output terminal to the ammeter if you have one, the same terminal that was used in the generator charging circuit. If you are changing from positive to negative ground then reverse the ammeter terminals from their original locations
#2 The polarity reversing switch was mounted on the starter, and most of them have been removed and discarded, it proved to be unnecessary and just one more thing to go wrong in the primary ignition circuit.
#3 You should not require anything other than the internally resisited coil, if you are going to run points you could get a condensor for a twelve volt application (in some cases they were the same for six or twelve volt), hope that helps.

Re: 12v Alternator converstion and some misc questions
3B #789470 Mon Oct 17 2011 05:06 AM
Joined: Apr 2011
Posts: 96
akguy34 Offline OP
Wrench Fetcher
Thank you very much I'll try and rewrite my wiring diagram to discard the unnessasary parts and fix my mistakes.

Re: 12v Alternator converstion and some misc questions
akguy34 #790579 Thu Oct 20 2011 04:54 PM
Joined: Jan 2000
Posts: 124
Shop Shark
If you have a true-one wire alternator than you cannot use the DA Plug. The advantage of using a 2-wire alternator and a DA Plug is that you will have a charging output at engine idle and low rpms. The yellow wire of the DA Plug is called the "exciter" wire and send a little bit of battery current to the alternator when you turn on the ignition switch so the alternator will begin charging as soon as the engine is started...regardless of the idle speed of the engine. A one-wire alternator typically does not have much of an output below 1200 rpms engine speed and your old truck does not idle at the 1200 rpms that a one-wire alternator was designed for. That is why a 2-wire alternator works better in older vehicle applications.When one-wire alternators were introduced they were originally for racing applications that ran only ignition and electric fuel pumps etc. By that time most everything was V8 powered and had idle speed of around 1200 rpms so that is the speed one-wire alternators were designed to begin charging. A one-wore alternator will usually not begin charging until you exceed the 1200 rpms cut-in speed of the alternator. Sometimes they will "drop out" or quit charging if the rpms get to slow like at a stoplight at night. You will notice it acting like an old generator charging system. Not a big deal and once the rpms come up the alternator will begin charging again. You just need to understand what is going on.....thanks Randy

Re: 12v Alternator converstion and some misc questions
fifthave #790623 Thu Oct 20 2011 07:23 PM
Joined: Sep 2001
Posts: 30,152
ace skiver


There is no way that I would disagree with you. However, I have a one-wire alternator that I have used for about 14 years. It "gets excited" at about 800-900 RPM and then shows charging even at idle (~500 rpm). Is that possible or am I misreading something?

Tim []
1954 3106 Carryall Suburban [] - part of the family for 49 years
1954 3104 5-window pickup w/Hydra-Matic [] - part of the family for 15 years
- If you have to stomp on your foot-pedal starter, either you, or your starter, or your engine, has a problem.
- The 216 and early 235 engines are not "splash oilers" - this is a splash oiler. []
Re: 12v Alternator converstion and some misc questions
tclederman #790629 Thu Oct 20 2011 07:32 PM
Joined: Jul 2011
Posts: 55
Wrench Fetcher
Possibly someone mounted a smaller pulley on it in order to make it spin faster?

Re: 12v Alternator converstion and some misc questions
EricJ #790703 Thu Oct 20 2011 11:17 PM
Joined: Jan 2000
Posts: 124
Shop Shark
The pulley size does make a difference as does the type of regulator they use and the air gap between the rotor and stator. You do typically get more amperage output from a two wire alternator as compared to a one wire at low engine rpms which is why most cars and trucks were built that way from the factory. Also one wire alternators have a constant internal electrical draw (about the same as a digital clock) so if you drive it every day or so life is good. If the truck sits in storage for a month or so you might have a dead battery unless you use a master switch or disconnect the battery (which are good ideas) But hey in your case if it is working...enjoy the ride. The trucks typically do not have a very high electrical load which also helps. I am just trying to help everyone understand the difference between the two types so when you shop for an alternator you know what you are buying.

Thanks Randy

Re: 12v Alternator converstion and some misc questions
fifthave #790875 Fri Oct 21 2011 04:24 PM
Joined: Feb 2004
Posts: 20,608
Once a 1-wire setup kicks in by goosing the throttle, it will continue to charge at lower RPM. The excitation is a one-shot situation, not something that requires the speed to be held above a certain level to continue to flow current. I really can't see the reason to use a single-wire hookup- - - -just use the alternator the way it was intended to be, and run one or two extra wires. The design of the internal regulator makes a big difference in how the alternator functions, as there have been at least three variations I've encountered over the past 30+ years.

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