Corvair Forum

While I am workingwith an alternator install, I found where I had posted this on the other forum and figured it could help others on this forum.

I was asked if there was a procedure to convert the 10DN externally regulated alternator to a 10SI internally regulated alternator. I look around and could find no simple step by step procedure for this request, I made this procedure, so he could quickly accomplish the project.

If any one wants the procedure pdf file, send me a pm with an email address.

Note: Procedure will convert a vehicle with a externally regulated alternator (10DN) to an internally regulated alternator (10SI).

1. Disconnect battery cables.
2. Loosen adjustable idler pulley and remove belt from idler pulley and alternator.
3. Remove connector from alternator.
4. Remove battery 10 gauge red wire from alternator. Return hardware to terminal post.
5. Remove hardware from rear support brace at alternator and engine. Discard brace and hardware from upper attach point. Retain hardware at engine.
6. While supporting alternator, remove hardware securing alternator to engine. Remove alternator. Place alternator and hardware on bench.
7. On 10DN alternator perform the following:
a. Remove fan, using 15/16 socket and air impact wrench. Hold fan with thick rag. Remove fan, nut, washer and spacer.
b. Remove 4 housing screws and place aside.

Caution: Do not rotate housings in next step!

c. Separate housings, keeping rotor with rear housing (larger piece). Put rear housing aside, as it will not be used.
d. Clean front housing thoroughly.
e. Inspect bearing/bushing in front housing for wear and/or damage. Replace, if needed.
8. On 10SI alternator, perform the following:
a. Remove fan. Use 15/16 socket and air impact wrench. Hold fan with thick rag. Remove fan, nut, washer and spacer. Put fan aside, as it will not be used.
b. Remove 4 housing screws and place aside.
Caution: Do not rotate housings in next step!
c. Separate housings, keeping rotor with rear housing (larger piece). Put front housing aside, as it will not be used.
d. Place 10DN alternator front housing onto 10SI alternator rear housing. Ensure rear housing 2 terminal connector is at 9 o’clock position with front housing mounting lugs at bottom.
e. Install 4 housing screws and torque bolts to 48 in-lbs. This is max torque for aluminum installation.
f. Install spacer, lock washer and fan. Torque to 40 – 60 ft-lbs. If using a crows foot, use calculation to lower the torque value applied, due to torque wrench offset from shaft centerline.
9. Install modified 10SI alternator with hardware. Torque bolts to specified value in Corvair Shop Manual.
Note: A new longer replacement rear support brace will need to be made to fit the new alternator to engine configuration
10. Install replacement rear support brace, as follows:
a. At engine shroud, position brace at shroud/head position.
b. Install bolt and snug bolt down. Support brace bolt should be snug to keep support brace upright to alternator, but allow movement of brace.
c. Align rear support brace to back of alternator brace mount point.
d. Install bolt with flat washer and lock washer through support brace. Slide spacer onto bolt and thread into alternator brace support mount point. Torque bolt to specified value in Corvair Shop Manual.
e. Torque shroud/head brace bolt to specified value in Corvair Shop Manual.
11. Connect alternator power lead to alternator single post terminal.
12. Modify alternator signal lead connector (2 wire) in one of the following methods:
a. Plug replacement:
1) Using terminal removal tool, remove wire from square plug. Insert blue wire into rectangular plug left side having lock positioned to the top.
2) Using terminal removal tool, remove wire from square plug. Insert blue wire into rectangular plug left side having lock positioned to the top.
3) Slide plug into the alternator and lock in place.
b. Adapter cable installation:
1) Connect adapter cable square plug to alternator cable square plug.
2) Slide adapter cable rectangular plug into the alternator and lock in place.
13. Remove all wires at voltage regulator.
14. Remove hardware securing voltage regulator. Remove voltage regulator. Set voltage regulator and hardware aside, as it will not be used.
15. Modify voltage regulator wiring in one of the following methods:
a. Permanent wiring modification:
1) Cut terminals from all regulator wires.
2) Cut blue and brown wires to a suitable length to secure in harness. Strip each wire and splice the together with an environmental splice.
3) Cut red and black/white wires to a suitable length to secure in harness. Strip each wire and splice the together with an environmental splice.
4) Secure wires to harness.
b. Adapter cable installation:
1) Connect regulator jumper plug to regulator plug. Push jumper in securely.
2) Secure jumper and wiring to harness.
16. Secure signal wiring harness to bottom of alternator. Use on small ty-wrap routed through cooling holes to make a loop and engage ty-rap locking strip. Use second ty-rap around harness and pass through the loop of the first ty-rap. Line the harness and ty-raps up, so harness is not stretched tight at connector. Tighten second ty-wrap around harness, then pull first ty-rap so cable is snug on alternator.
17. Connect 10 gauge red wire to alternator post and tighten securely.
18. Check Battery Voltage is 12v.
19. Connect Battery. Ensure no unusual indications are observed on car.
20. Turn Ignition On. Ensure no unusual indications are observed on car.
21. Start Engine. Ensure GEN light goes out. Ensure no unusual indications are observed on car.
22. Check Voltage at Battery. It should be 14 – 14.7 volts.
23. Turn off Engine. Ensure Engine will shut down.

PARTS LIST
Alternator:
AC Delco 10SI. It will be modified, using parts from the 38 or 45 amp Corvair alternator.

Note: Try to locate a tractor capable 10SI alternator. It has a lower regulator rpm kick in point. Great for manual transmission cars on hot days. No need to accelerate engine to get alternator charging battery.

Alternator voltage sense harness modification:
GM Internally Regulated Alternator Connector (Dorman 85841)

Alternator Conversion Modification:
Conversion Wiring Adapter Kit 27555

Note: Try to locate a tractor capable 10SI alternator. It has a lower regulator rpm kick in point. Great for manual transmission cars on hot days. No need to accelerate engine to get alternator charging battery.

Al, that golden nugget is appreciated!

Thank you ], Ken.

These photos of the mounting will probably help also

Next time, I will cut red lead back and install a new ring terminal. Just to get rid of the sharp bend.

kmart356 wrote: ↑Sat Mar 01, 2025 6:37 am

Note: Try to locate a tractor capable 10SI alternator. It has a lower regulator rpm kick in point. Great for manual transmission cars on hot days. No need to accelerate engine to get alternator charging battery.

Al, that golden nugget is appreciated!

Sorry this is incorrect information --- The "tractor" 10SI internal voltage regulator circuit is ONLY used for ONE WIRE installations to self energize the alternator (you still have to rev up the engine a little). Once the alternator gets "energized" it will stay running even at low RPM. All the talk about "hot day" issues if incorrect. I've converted a number of Corvairs to 10SI and my cars have A/C and they idle low on hot days and the standard 63 Amp 10SI works fine. If didn't the "GEN/FAN" lamp would illuminate and it DOES NOT.

The "normal" automotive 10SI energizes when you turn on the ignition key via the warning lamp. So no need for a "tractor" 10SI --- yet this "Corvair Myth" persists.

Lane66Monza wrote: ↑Sat Mar 01, 2025 5:39 am While I am workingwith an alternator install, I found where I had posted this on the other forum and figured it could help others on this forum.


PARTS LIST
Alternator:
AC Delco 10SI. It will be modified, using parts from the 38 or 45 amp Corvair alternator.

Note: Try to locate a tractor capable 10SI alternator. It has a lower regulator rpm kick in point. Great for manual transmission cars on hot days. No need to accelerate engine to get alternator charging battery.

Alternator voltage sense harness modification:
GM Internally Regulated Alternator Connector (Dorman 85841)

Alternator Conversion Modification:
Conversion Wiring Adapter Kit 27555

65 - 69 Corvair Alternator (Internally Regulated) - Wiring Diagram.jpg

10DN to 10SI Alternator (IR) Conversion Procedure.pdf

Great information Al - BUT THERE IS NO DIODE between the ignition key and warning light. Years ago a number of use discussed this with you. So please correct your diagram - thanks.

There NEVER was a diode in the Corvair wiring harness (except on CORSA for the over heat buzzer). Some claim it is needed, but NO it is not. The old claim was when you turned the key OFF the alternator would feed back through the warning light and out to the coil so engine would not shut off. I HAVE NEVER SEEN THIS ISSUE. I have done a number of 10SI conversions on LM and EM cars and NEVER used a diode.

I'm not sure how this "must use a diode" thing got going, but I suspect someone had a wiring issue and fixed it with a diode. When a 10SI installation is done correctly, then a diode IS NOT NEEDED!! Yes the alternator has a little feed back to the warning lamp when you turn off the engine, but that it is not enough to keep the ignition coil working ON A STANDARD CORVAIR. I did a load calculation to confirm this.

Heck, I though I took that ought of all the diagrams that got out there..

Yes, there are 3 wire tractor 10SI alternators. I have 1 on each of my 2 Corvairs engines, 1 on my Camaro engine, 2 in my spares for the Corvair and Camaro. Just got to buy the one with the cap covering the 2 terminal plug. Remove cap and it goes to work as a 3 wire when plugged in.

Lane66Monza wrote: ↑Sat Mar 01, 2025 7:11 pm Heck, I though I took that ought of all the diagrams that got out there..

Yes, there are 3 wire tractor 10SI alternators. I have 1 on each of my 2 Corvairs engines, 1 on my Camaro engine, 2 in my spares for the Corvair and Camaro. Just got to buy the one with the cap covering the 2 terminal plug. Remove cap and it goes to work as a 3 wire when plugged in.

That is interesting Al. The original "tractor" or industrial 10SI did not have the ability to plug in the other two wires. I suspect now it is an aftermarket board with an internal jumper added. That is what some places do to make it a "one wire" setup. I stick with the 63Amp unit because of it's high output at low RPM relative to the other 10SI units --- HOWEVER that is based on the original DELCO units. Of course the old 10SI Delco parts are long gone. Like the "HEI" parts most of it is off shore copies. Quality unknown.

At this point all we can do is use what is available and hope for the best.

Mine are all 63 amp 1OSI lower RPM kick in units, i.e. tractor units, or ones best for Vairs with manual transmissions. PG equipped cars it doesn't matter since they have a higher idle rpm.


You are probably right that all 10SI alternators are now kicking in at 600 engine rpm versus the 800 that was seen 10 years ago. I just like to try to find ones that sellers' documents the lower kick in rpm versus ones that just state they are 10SI alternators.

I got the right diagram in the original post. I also updated it to reflect permanent change to 10SI or being able to revert back to 10DN with the M&H Electrical Conversion Wiring Adapter Kit #27555 ($34) or the American Autowire Wiring Adapter Kit #27555 ($46). Kits were $26, 5 years ago.

I am glad you find the instructions useful. Procedure has done its job of making the alternator model changeover procedure easier and less daunting to anyone attempting it.

Using an electric or air impact wrench to get the nut off is the recommended tool. I usually slip ratchet straps under the fan. Then Donna lifts the alternator up slightly, so it can drop on its weight, when fan comes loose. I pull up on the straps, while gently tapping the shaft with a plastic mallet. Usually it is 2 or 3 taps and the fan is off. Doing the same method while holding straps and letting alternator drop about inch onto a thick foam block can be the one person method.

The photo shows what I use to torque the nut back on. You have to have a torque wrench capable of CCW torqueing.



These are the Delco instructions for the nut's torque value. You will get comments that using the impact wrench to put the nut back on will work. I like knowing what the actual torque is when installing the nut. This is a high torque value to apply.
Delco specifies a torque for a reason.

Another BOT. Dwayne21.

I will check each name for when joined from now on, if I don't know the name. I will stop answering those with new registrations. Just wasting my time. A real new member has to prove they are not a bot in some manner that a computer can't generate the info they chose to authenticate themselves.

Lane66Monza wrote: ↑Fri Apr 11, 2025 2:38 am Another BOT. Dwayne21.

I will check each name for when joined from now on, if I don't know the name. I will stop answering those with new registrations. Just wasting my time. A real new member has to prove they are not a bot in some manner that a computer can't generate the info they chose to authenticate themselves.

Probably some enterprise is trying to see how well their A.I. replies appear "human". Using us to "train" their system.

JUST BECAUSE YOU ARE PARANOID DOESN'T MEAN THEY ARE NOT OUT TO GET YOU!