One wire Alternator

naa10104 · Mar 17, 2015

Posted about this several months ago ... getting ready to do the install but am now getting conflicting advice on how to do it. I have a 73 Mustang Convertible, 351C, no A/C, auto, stock radio. I purchased a Summit one wire alternator, 100 Amp, I also have a wire kit that has 8 and 10 gauge wire.

My original research indicated that I run either the 8 or 10 gauge wire directly from the new alternator to the positive terminal of the battery. There is a grounding lug on the alternator which I am told I should ground to the body of the car just to be safe. The original wiring that was connected to the old alternator can either be completely removed or secured out of the way. The wiring at the voltage regulator should be disconnected, (although this may cause the charging idiot light to either glow continually or not function.) Do I need to place an inline fuse between the battery and new alternator ? If so, what amperage should the fuse be ?

One person suggested that I wire as above but also leave all the old wiring connected at the alternator as well as the regulator. Another said that there has to be a connection to the fuse block of the car. At any rate, I want to this correctly/safely, but not over do it. I would really appreciate some clear advice on how to accomplish this ... thanks

Jeff73Mach1 · Mar 17, 2015

I just did mine last month. I used a 130 amp 3 G alternator. The excite wire is routed to the same post as the charge wire and the alternator begins to charge after it first turns 1400 rpm and then charges until the car is shut off.

I used 2 gauge from the alternator to a 150 amp mega fuse which I placed where the former junction block was for the ammeter

and then ran to the starter relay solenoid (hot side, so effectively to the battery.) I removed the VR and the wiring. There were 2 hot wires that I taped off.

I have gauges not warning lights, so I can't comment on the alternator light, except to say I have read there is a way to wire it

here is one way http://www.tuffstuffperformance.com/pdf/1-wire_alternator_instructions.pdf

if it is a gm style you might want to read this

http://bob_skelly.home.comcast.net/~bob_skelly/alternator_conversion/wiring_alternator1.html

Overall it is an easy upgrade.

naa10104 · Mar 17, 2015

I just did mine last month. I used a 130 amp 3 G alternator. The excite wire is routed to the same post as the charge wire and the alternator begins to charge after it first turns 1400 rpm and then charges until the car is shut off.

I used 2 gauge from the alternator to a 150 amp mega fuse which I placed where the former junction block was for the ammeter

and then ran to the starter relay solenoid (hot side, so effectively to the battery.) I removed the VR and the wiring. There were 2 hot wires that I taped off.

I have gauges not warning lights, so I can't comment on the alternator light, except to say I have read there is a way to wire it

here is one way http://www.tuffstuffperformance.com/pdf/1-wire_alternator_instructions.pdf

if it is a gm style you might want to read this

http://bob_skelly.home.comcast.net/~bob_skelly/alternator_conversion/wiring_alternator1.html

Overall it is an easy upgrade.

thanks very much I will check out the links !

jbojo · Mar 17, 2015

So from the alternator you want to go to a fuse/CB and then to the positive side of the battery. The fuse should be at least 100A but you want a buffer for short spikes if that should happen. The alternator will not be putting out 100a at all times so only if there is a high demand a 100A fuse would work but I would probably use 110A. I also used a circuit breaker but many prefer fuses so your preference there.

On my build I removed the regulator and the wires for a cleaner look as it is no longer needed however the alt light will no longer work. You will need to use a voltmeter if you want to see if the battery is charging and must be on a switched circuit. For me I had my amp meter converted to a voltmeter so that I could monitor the charging system. Its a pretty simple conversion so it should not take more that 2 hours.

Lastly make sure that the battery is disconnected when doing this and that the ground wire on the alternator has a good ground connection.

EDIT: Jeff replied while I was writing this so its basically the same

naa10104 · Mar 17, 2015

So from the alternator you want to go to a fuse/CB and then to the positive side of the battery. The fuse should be at least 100A but you want a buffer for short spikes if that should happen. The alternator will not be putting out 100a at all times so only if there is a high demand a 100A fuse would work but I would probably use 110A. I also used a circuit breaker but many prefer fuses so your preference there.

On my build I removed the regulator and the wires for a cleaner look as it is no longer needed however the alt light will no longer work. You will need to use a voltmeter if you want to see if the battery is charging and must be on a switched circuit. For me I had my amp meter converted to a voltmeter so that I could monitor the charging system. Its a pretty simple conversion so it should not take more that 2 hours.

Lastly make sure that the battery is disconnected when doing this and that the ground wire on the alternator has a good ground connection.

EDIT: Jeff replied while I was writing this so its basically the same

Thanks again to both ... great information !

So from the alternator you want to go to a fuse/CB and then to the positive side of the battery. The fuse should be at least 100A but you want a buffer for short spikes if that should happen. The alternator will not be putting out 100a at all times so only if there is a high demand a 100A fuse would work but I would probably use 110A. I also used a circuit breaker but many prefer fuses so your preference there.

On my build I removed the regulator and the wires for a cleaner look as it is no longer needed however the alt light will no longer work. You will need to use a voltmeter if you want to see if the battery is charging and must be on a switched circuit. For me I had my amp meter converted to a voltmeter so that I could monitor the charging system. Its a pretty simple conversion so it should not take more that 2 hours.

Lastly make sure that the battery is disconnected when doing this and that the ground wire on the alternator has a good ground connection.

EDIT: Jeff replied while I was writing this so its basically the same

Click to expand...

Thanks again to both ... great information !

ANY ONE KNOW WHICH WIRE IN THE ORIGINAL ALTERNATOR WIRING WOULD RUN THE IDIOT LIGHT ON THE DASH ? THANKS AGAIN.

midlife · Mar 17, 2015

The green/red wire that ends up in the 1 wire but 2 pin plug IIRC.

naa10104 · Mar 18, 2015

The green/red wire that ends up in the 1 wire but 2 pin plug IIRC.

Thanks very much

naa10104 · Mar 19, 2015

The green/red wire that ends up in the 1 wire but 2 pin plug IIRC.

Installed the new 100 AMP one wire alternator today, seems to work fine. Ran a new 8 gauge wire from the positive lug on the ALT to the POS terminal of the ignition solenoid. Ran a new 8 gauge ground from the body of the ALT to the frame of the car for ground. I removed the entire original harness that ran from the ALT to the Regulator. There was no red/grn wire as described at the original alternator. I included a photo of the original harness, (left side is what was connected to the ALT.) Also a picture of the Regulator/Solenoid. Curious if anyone can give me more information on the correct wire to connect to the new alternator so the Charge Idiot light still functions. Thanks very much.

Steve

jbojo · Mar 19, 2015

I don't believe that you can get the Alt light to work without the regulator. I believe that if the regulator doesn't detect the alternator charging it turns on the light. It sort of works light a relay. Looking at the wiring diagram so I am trying to figure out that circuit works.

naa10104 · Mar 19, 2015

I don't believe that you can get the Alt light to work without the regulator. I believe that if the regulator doesn't detect the alternator charging it turns on the light. It sort of works light a relay. Looking at the wiring diagram so I am trying to figure out that circuit works.

Hello,

Thanks for the reply, I was in a hurry today, but I think the light does not work at all now. When you turn the ignition on the "charge" light does not illuminate at all. I tried to find the red/green wire the other member spoke of but there was not one at the old alternator. There are is one at the ignition solenoid, not sure if this is the one he is speaking of.

jbojo · Mar 19, 2015

I don't believe that you can get the Alt light to work without the regulator. I believe that if the regulator doesn't detect the alternator charging it turns on the light. It sort of works light a relay. Looking at the wiring diagram so I am trying to figure out that circuit works.

Click to expand...

Hello,

Thanks for the reply, I was in a hurry today, but I think the light does not work at all now. When you turn the ignition on the "charge" light does not illuminate at all. I tried to find the red/green wire the other member spoke of but there was not one at the old alternator. There are is one at the ignition solenoid, not sure if this is the one he is speaking of.

The light not working is what I would expect. Took a look at the wiring diagram and there is a relay in the regulator that would supply pwr to the light when Alt is not working.

There is another relay that would provide pwr to the alternator fields that would turns it on/off. There are resistors in the diagram but no values so it hard to determine the exact operation but it appears to be like this:

At around 13.5v the regulator would supply power to the Alt fields to turn the alternator on and charge the battery. At around 14.5v the regulator will stop supplying pwr to the fields and it would stop charging. If battery voltage is below 13.5v and alt is not charging then the regulator will supply pwr to the alt light to tell you there is a problem.

The drawback with the light is that it won't illuminate until the system has failed. With a voltmeter you can sort of monitor the condition of the charging system.

There should be 2 wires with a green base color and red stripe on the connector for the regulator. Wiring diagrams are sometimes not correct but this is what mine indicates.

naa10104 · Mar 19, 2015

The green/red wire that ends up in the 1 wire but 2 pin plug IIRC.

Hello,

What does IIRC stand for ? Is there any place/wire at the starter relay that I can splice into ? I have removed the entire harness that ran between the old alternator and the voltage Regulator. There is a red/green wire that plugs into the starter relay. My new alternator has a specific plug to utilize for running the idiot light I just need to know which wire to connect it with. Thanks very much !

I don't believe that you can get the Alt light to work without the regulator. I believe that if the regulator doesn't detect the alternator charging it turns on the light. It sort of works light a relay. Looking at the wiring diagram so I am trying to figure out that circuit works.

Click to expand...

Hello,

Thanks for the reply, I was in a hurry today, but I think the light does not work at all now. When you turn the ignition on the "charge" light does not illuminate at all. I tried to find the red/green wire the other member spoke of but there was not one at the old alternator. There are is one at the ignition solenoid, not sure if this is the one he is speaking of.

Click to expand...

The light not working is what I would expect. Took a look at the wiring diagram and there is a relay in the regulator that would supply pwr to the light when Alt is not working.

There is another relay that would provide pwr to the alternator fields that would turns it on/off. There are resistors in the diagram but no values so it hard to determine the exact operation but it appears to be like this:

At around 13.5v the regulator would supply power to the Alt fields to turn the alternator on and charge the battery. At around 14.5v the regulator will stop supplying pwr to the fields and it would stop charging. If battery voltage is below 13.5v and alt is not charging then the regulator will supply pwr to the alt light to tell you there is a problem.

The drawback with the light is that it won't illuminate until the system has failed. With a voltmeter you can sort of monitor the condition of the charging system.

There should be 2 wires with a green base color and red stripe on the connector for the regulator. Wiring diagrams are sometimes not correct but this is what mine indicates.

Thanks very much for your efforts ... I have removed the entire original wire harness that ran from the old alternator to the voltage regulator. It consisted of 3 connections to the old alternator, the plastic plug that went into the side of the voltage reg., two plastic plugs, and one male into female single plug. All that is left are the connections to the starter relay. There is at least one red and green wire there. Don't know if this helps any. Thanks again.

midlife · Mar 19, 2015

IIRC: If I remember correctly.

Yes, follow the green/red wire that comes out of the voltage regulator and you'll see a strange two pin but one wire plug that mates to the headlight harness if it is a 72 or 73. On a 71, it is a single pin wire. I thought this wire goes to the alternator harness, as it usually does for the 65-70 years. It is NOT the green/red wire at the starter solenoid: that should be a red/green or a brown wire at the rearward post.

jbojo · Mar 19, 2015

For a 73 look for the connector RH fender apron side (rear). There should be a 2 pin connector but only 1 pin is actually used and it should be that green/red wire, at least that what the schematic says. Also look at the regulator wiring harness and you should see that wire there too. Mine had the ammeter so its different but I would think that the connector for the light should still be there unless the wiring harness is different for a light and Gauge. I'll go out and see if I can locate it.

dabowman · Mar 20, 2015

Just to add to this tread, I saw this adapter at CJ Pony parts for adding a 3G alt to a 1G system. If someone wanted to maintain the "factory look" and connections. Anyone use one of these or heard of these?

http://www.cjponyparts.com/pa-performance-alternator-conversion-kit-allows-use-of-3g-130-amp-alternator-1965-1985/p/ALTCK/

jbojo · Mar 20, 2015

Steve,

On the wiring harness picture you posted the connector on the right is the voltage regulator connector. The first wire (green with red stripe) at the top of that connector is the one that goes to your light. When the ignition switch is on but motor not running it sends 12v to the light and enters the regulator (terminal "I") which provides a ground and the light goes on. The next wire on the connector (should be two wires) 1 has the noise suppression capacitor and the other goes to the ignition switch (Terminal "A+" on the regulator). When the motor is starting and the alternator output reaches 3v the field relay closes the in the regulator allowing 12v in through terminal "A+" effectively cancelling out the current flow though the indicator that's coming into terminal "I" and the light goes off.

So if you trace those 2 wires on the connector to where you disconnected them from your main engine compartment harness that will tell you what wires you need to use to get the light working. You also mentioned that your new alternator had a connection to make the light work, do you have a electrical schematic of that alternator?

If that light connector on the alternator doesn't make the indicator work properly I think I know how you can make that light work by adding a relay but I need to see a schematic of that alternator to see how that light connection works. This is probably more info than you wanted but your questions motivated me to learn more about how the charging system works so it was a good learning experience for me.

naa10104 · Mar 20, 2015

Thanks for all the information .... appreciate it. Might be a few weeks before I can get back into this but I will post what I find out. I will attach the instructions for the new 1 wire alternator which shows the connection for the dash idiot light. I have already installed a factory plug in the new alternator as instructed and have it ready to connect to the correct wire when I figure that out. I have to look at the voltage regulator again and see what wires are still connected to it and where they go. At this point my intention is to remove the VR and store it. No need for it now and it will clean up the engine compartment. Thanks again !

Thanks for all the information .... appreciate it. Might be a few weeks before I can get back into this but I will post what I find out. I will attach the instructions for the new 1 wire alternator which shows the connection for the dash idiot light. I have already installed a factory plug in the new alternator as instructed and have it ready to connect to the correct wire when I figure that out. I have to look at the voltage regulator again and see what wires are still connected to it and where they go. At this point my intention is to remove the VR and store it. No need for it now and it will clean up the engine compartment. Thanks again !

1-wire_alternator_instructions.pdf

jbojo · Mar 20, 2015

For the light connection on the alt I would expect to see a ground when the key is on and motor off and an open when the motor is running. You would just need to trace the green/red wire from the regulator connector back to where it connects to the main engine compartment harness. Then you can remove the regulator harness and connect green/red wire on the main harness to the alternator terminal. I would do the alternator check before making the final connection to ensure that R terminal works as expected.

naa10104 · Mar 20, 2015

Steve,

On the wiring harness picture you posted the connector on the right is the voltage regulator connector. The first wire (green with red stripe) at the top of that connector is the one that goes to your light. When the ignition switch is on but motor not running it sends 12v to the light and enters the regulator (terminal "I") which provides a ground and the light goes on. The next wire on the connector (should be two wires) 1 has the noise suppression capacitor and the other goes to the ignition switch (Terminal "A+" on the regulator). When the motor is starting and the alternator output reaches 3v the field relay closes the in the regulator allowing 12v in through terminal "A+" effectively cancelling out the current flow though the indicator that's coming into terminal "I" and the light goes off.

So if you trace those 2 wires on the connector to where you disconnected them from your main engine compartment harness that will tell you what wires you need to use to get the light working. You also mentioned that your new alternator had a connection to make the light work, do you have a electrical schematic of that alternator?

If that light connector on the alternator doesn't make the indicator work properly I think I know how you can make that light work by adding a relay but I need to see a schematic of that alternator to see how that light connection works. This is probably more info than you wanted but your questions motivated me to learn more about how the charging system works so it was a good learning experience for me.

Hello ... here is the info. on the one wire alternator and how to connect the idiot light ... Thanks

1-wire_alternator_instructions.pdf 1-wire_alternator_instructions.pdf

One wire Alternator

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