ATC King
11-30-2020, 10:31 AM
There are some other members who have older vehicles, so I'm throwing this together for anyone else who is still running an external reg.
I've been meaning to do this on my '79 F150 for a while, but just now got around to it. The old external system was still working fine, but it was only 42 amp and I also wanted the space on the fender for something else.
This swap can simplify the wiring, declutter the engine compartment, increase charging output, and make use of a more modern, readily available alternator.
I'm using a Delco 12Si, but this is the same for the 10Si and maybe some others. The voltage sensing wire is being used, along with the warning light. One wire alternators are not good to use on much of anything but a tractor; the sensing wire is very important for a stable system.
The Delco 12Si comes in three amperages (there are some higher output aftermarket ones). 78 is the lowest and that's what I used, because I had it on hand.
First is changing the harness. On a '79 F150, this is simple because it's only a short, individual harness. I made a new one, only using the old two wire plug from the original. The parts store didn't have any of those in stock, but they did have new connectors for the Delco alternator. I used 10 gauge wire, which is a minimum. Any higher capacity alternator, and I would've went with 8 gauge as a precaution. It's not only the length and gauge of wire that determines how many amps it can handle, but also temperature, and under hood temps can get pretty high, especially with a powerful engine and/or headers. Keep that all in mind when calculating what gauge charging wire to use.
Old harness:
265376
New harness:
265377
My old harness had a two wire plug, which is a standard type of old Ford electrical connector. The only wire actually used is the Grn/R one, which is for the warning light. This is hooked to the #1 terminal on the Delco plug. The white/blk wire was only for the old alternator to supply the (now gone) electric choke. I taped both into the harness just to keep from having a single wire hanging out, it's not hooked to anything.
On some systems, a diode will have to be placed in the warning light wire. The warning light is turned off when the alternator is working, by sending voltage back to the bulb, which cancels out the circuit and turns the bulb off. This means that circuit can feed electricity back into things, depending on how it's set up. From experience, this is probably more true for points style ignitions and they way they are normally wired.
Without the diode, or changing the switched wiring of the system, enough power will be fed back to keep the engine running even after the ignition switch is turned off. I've experience this myself, and it's a head scratcher if you don't already know. In my '79 F150 application, that was not an issue and there was no need for a diode or ignition wiring alterations.
265382
These types of products can be bought, if not wanting to make.
https://www.ebay.com/itm/CHEVY-DELCO-ALTERNATOR-HARNESS-ANTI-FEEDBACK-DIODE-10SI-12SI-15SI-27SI-wire-/201247906131
265378
Sometimes, the charging harness is grafted into the main harness and it's easier to use jumpers on the old external reg connector. If someone doesn't want to make simple jumpers on their own, or wants a more finished looking product, a plug in jumper is available for some applications too. This makes everything plug and play.
https://www.speedwaymotors.com/Alternator-Conversion-Kit-External-to-Internal-Regulator-Harness,116911.html?sku=92612557&msclkid=40712e96806d1cb6c7d4715385fcf848&utm_source=bing&utm_medium=cpc&utm_campaign=SMI%20-%20Shopping%20(CSE)%20(Bing)&utm_term=4577404348890847&utm_content=All%20Products%20(Feb28_2020)
https://content.speedwaymotors.com/ProductImages/92612557_L_ee5486ac-5025-4e25-96f1-c7a63455a349.webp
Back to the #1 and #2 terminals on the Delco plug. #1 again being for the warning light, and #2 for the sensing wire. The #2 wire can be switched power or it can be full-time. Either way is fine. GM actually has this wire hot, full-time, on some of their vehicles, which is not a problem. The alternator senses when it's in operation, so this isn't going to drain the battery or harm anything.
It is possible to just hook the #2 wire back on to the alternator battery lug, but that won't sense system voltage further down the line, which means the voltage at the alternator could be correct, but on down the line it would be lower. It's best too attach the sensing wire to a main junction, where other systems tie in. Ford often used a remote starting solenoid, which made my swap easier, because this is also a junction for the other wiring systems. On the new harness I made, the #2 wire is run to the same solenoid lug as the charging wire. It all depends on where a system junction is and is going to be different for each application.
Some of the following pictures show two different 12Si alternators. I had one sitting around that I initially installed, only to find out it was bad. The other one I robbed off of my car, and ordered a higher amp one to go back on it, keeping this one on my truck. 78 amps should be enough for my pickup which doesn't have power seats, windows, A/C, and other creature comforts to suck more power.
Comparing the old to new.
265380265381
In my application, I had to drill the main mounting hole to 7/16". I think the Delco Si alternators are metric, so the hole was just a bit too small.
265379
This swap was also brought some peace of mind because of the headers I'm using, the original alternator bolt couldn't be removed without removing the entire bracket. The Delco mount is narrower and uses spacers to take up the gap, which means the bolt can move back far enough to remove the alternator without removing the entire bracket. This will make any roadside repairs much easier now.
Pictures before and after:
265383265384265385265386
Some of what finally spurred this on is I needed a location to mount a small super capacitor module and the external reg was right where I want to put it. In the end, I'm not cleaning up the engine compartment, I'm just rearranging it, for MORE POWER. :w00t: This 12Si also charges better at low RPM than the original alternator.
I've been meaning to do this on my '79 F150 for a while, but just now got around to it. The old external system was still working fine, but it was only 42 amp and I also wanted the space on the fender for something else.
This swap can simplify the wiring, declutter the engine compartment, increase charging output, and make use of a more modern, readily available alternator.
I'm using a Delco 12Si, but this is the same for the 10Si and maybe some others. The voltage sensing wire is being used, along with the warning light. One wire alternators are not good to use on much of anything but a tractor; the sensing wire is very important for a stable system.
The Delco 12Si comes in three amperages (there are some higher output aftermarket ones). 78 is the lowest and that's what I used, because I had it on hand.
First is changing the harness. On a '79 F150, this is simple because it's only a short, individual harness. I made a new one, only using the old two wire plug from the original. The parts store didn't have any of those in stock, but they did have new connectors for the Delco alternator. I used 10 gauge wire, which is a minimum. Any higher capacity alternator, and I would've went with 8 gauge as a precaution. It's not only the length and gauge of wire that determines how many amps it can handle, but also temperature, and under hood temps can get pretty high, especially with a powerful engine and/or headers. Keep that all in mind when calculating what gauge charging wire to use.
Old harness:
265376
New harness:
265377
My old harness had a two wire plug, which is a standard type of old Ford electrical connector. The only wire actually used is the Grn/R one, which is for the warning light. This is hooked to the #1 terminal on the Delco plug. The white/blk wire was only for the old alternator to supply the (now gone) electric choke. I taped both into the harness just to keep from having a single wire hanging out, it's not hooked to anything.
On some systems, a diode will have to be placed in the warning light wire. The warning light is turned off when the alternator is working, by sending voltage back to the bulb, which cancels out the circuit and turns the bulb off. This means that circuit can feed electricity back into things, depending on how it's set up. From experience, this is probably more true for points style ignitions and they way they are normally wired.
Without the diode, or changing the switched wiring of the system, enough power will be fed back to keep the engine running even after the ignition switch is turned off. I've experience this myself, and it's a head scratcher if you don't already know. In my '79 F150 application, that was not an issue and there was no need for a diode or ignition wiring alterations.
265382
These types of products can be bought, if not wanting to make.
https://www.ebay.com/itm/CHEVY-DELCO-ALTERNATOR-HARNESS-ANTI-FEEDBACK-DIODE-10SI-12SI-15SI-27SI-wire-/201247906131
265378
Sometimes, the charging harness is grafted into the main harness and it's easier to use jumpers on the old external reg connector. If someone doesn't want to make simple jumpers on their own, or wants a more finished looking product, a plug in jumper is available for some applications too. This makes everything plug and play.
https://www.speedwaymotors.com/Alternator-Conversion-Kit-External-to-Internal-Regulator-Harness,116911.html?sku=92612557&msclkid=40712e96806d1cb6c7d4715385fcf848&utm_source=bing&utm_medium=cpc&utm_campaign=SMI%20-%20Shopping%20(CSE)%20(Bing)&utm_term=4577404348890847&utm_content=All%20Products%20(Feb28_2020)
https://content.speedwaymotors.com/ProductImages/92612557_L_ee5486ac-5025-4e25-96f1-c7a63455a349.webp
Back to the #1 and #2 terminals on the Delco plug. #1 again being for the warning light, and #2 for the sensing wire. The #2 wire can be switched power or it can be full-time. Either way is fine. GM actually has this wire hot, full-time, on some of their vehicles, which is not a problem. The alternator senses when it's in operation, so this isn't going to drain the battery or harm anything.
It is possible to just hook the #2 wire back on to the alternator battery lug, but that won't sense system voltage further down the line, which means the voltage at the alternator could be correct, but on down the line it would be lower. It's best too attach the sensing wire to a main junction, where other systems tie in. Ford often used a remote starting solenoid, which made my swap easier, because this is also a junction for the other wiring systems. On the new harness I made, the #2 wire is run to the same solenoid lug as the charging wire. It all depends on where a system junction is and is going to be different for each application.
Some of the following pictures show two different 12Si alternators. I had one sitting around that I initially installed, only to find out it was bad. The other one I robbed off of my car, and ordered a higher amp one to go back on it, keeping this one on my truck. 78 amps should be enough for my pickup which doesn't have power seats, windows, A/C, and other creature comforts to suck more power.
Comparing the old to new.
265380265381
In my application, I had to drill the main mounting hole to 7/16". I think the Delco Si alternators are metric, so the hole was just a bit too small.
265379
This swap was also brought some peace of mind because of the headers I'm using, the original alternator bolt couldn't be removed without removing the entire bracket. The Delco mount is narrower and uses spacers to take up the gap, which means the bolt can move back far enough to remove the alternator without removing the entire bracket. This will make any roadside repairs much easier now.
Pictures before and after:
265383265384265385265386
Some of what finally spurred this on is I needed a location to mount a small super capacitor module and the external reg was right where I want to put it. In the end, I'm not cleaning up the engine compartment, I'm just rearranging it, for MORE POWER. :w00t: This 12Si also charges better at low RPM than the original alternator.