By Geoffrey A. Johnson
The stock generator worked fine in early model ('60-64) Corvairs and still
does, just like countless other cars of
the era. There are definate advantages to an alternator though. So if opted
is a simple swap. There are several options in the conversion.
- Use an externally regulated 10DN Delco Alternator, this is the same as was
stock on late model Corvairs.
- Use an internally regulated 10SI or 12SI Delco Alternator off a slightly
product. These can be wired two ways, as outlined below. The second
approximates a one wire setup.
- A true one wire setup. Here a special self exciting regulator is installed
10SI style alternator. Control of the dash idiot light is lost if this is
- Something else. There surely are other ways this could be done,
these are the practical ways. Re-invent the wheel if you want.
Here is a diagram of the stock Corvair generator wiring
The most common method when converting an early model, and the one outlined
here, is to use the internally
10SI or 12SI. The 12SI is funtionally the same but does not have the ribs on
the case that the 10SI does and looks a little more stock. For a late model
Corvair I prefer to leave the unit stock for simplicity. You can order
a kit from a Corvair Vendor or do the conversion
yourself if you have the needed Corvair alternator specific parts. These
- The front half of a stock corvair alternator. This bolts directly to the
back half of the internally regulated unit.
- Acorrect Corvair alternator fan. The alternator when mounted on
a Corvair engine turns in the
direction from a standard GM alternator. This does not matter to operation
of the unit, but it is critical for air movement from the fan for cooling. A
bi-directional fan off of a marine use GM alternator will work as well as long
as the pulley and spacing are the same. The fan off the old generator can be
used as well in a pinch.
- A late model Corvair alternator adaptor. This is
adaptor that the alternator mounts too. The old one for the generator will not
work. This is the part bolted to to the engine that mounts the fuel pump and
oil filler as well.
You can get the internally regulated 10SI or 12SI GM alternator from an auto
parts store or a junkyard. They were used in many 70's and 80's GM applications
It is easiest to look
for a mid-seventies V8 GM application to ask for at the parts counter. Lester Interchange #7294 will get
you a 12SI rated at
94 amps. Look for one off of an '85 Buick Riviera. Not that you would ever
need that much. A note, heat generated by the alternator goes up with the square of amperage multiplied by ohms of
resistance. This means the higher the amperage the more heat.
A cheap route is to go to the junkyard to find an alternator core when
building one as opposed to buying new.
It is surprising to look through and see how many cars may have an almost new
alternator on them - a last ditch effort by the PO to save the car? Usually one can be found that has been recently refurbished.
For 10$ a piece
versus $80 at an auto parts store, this is quite economical, considering you will be throwing out most of the parts anyway.
To start off, swap the end housing of the
new alternator to the Corvair unit. It bolts together fairly easily.
You need to use the stock Corvair pulley and fan though to keep the cooling flow
It is often difficult to get the pulley nut off, and usually you need
an impact wrench. A chain wrench works very well if you have one. Once off replace the ball bearing in the Corvair housing with one off
the new alternator (even if new,
it is worth checking that the bearing has adequate grease, the sealed cap can be pried off with a sharp point, then pushes
back in place). Then put the new rotor in the Corvair housing. Keep the bearing
spacer rings in proper order.
When putting the two halves together use a paperclip inserted through the
hole in the back to hold the brushes
in place. Assemble it so that the two terminals face the back of the car
in the installed position. This is not an absolute, but allows for easy wire routing.
It should be self apparent to disconnect the battery before doing the
You can clip the wiring plug for the alternator off a car in the junkyard, or they can be purchased in the wiring section of any auto
Basically, you connect the old generator Armature wire ( the large brown wire on
armature terminal on the regulator ) to the Battery terminal on the Regulator.
Then connect the other end of it to the #2 terminal on the Alternator.
Note, the Alternator should be marked with a 1 and 2 cast into the housing
by the terminals.
A new #10 gauge red wire should then be run from the battery terminal on the
the battery terminal on the alternator. This is the main power output line.
I advise soldering the connectors for longevity.
The "field" wire can be cut, and used to connect to the #1 connector on the
alternator. As in diagram. Then clip the small 18 gauge brown wire off of the
middle terminal of the regulator (attached to the old armature wire,
presumably already moved to the Battery terminal).
Then clip the blue field wire end at the regulator and connect it to the small
brown clipped wire from the middle terminal. This is the the wire to the light
That is about it.
This is what the new wiring will look like.
This is a simpler (yet somewhat incorrect) way
to connect the wires, but all
contacts must be perfect,
and is not as accurate. That said, I have seen plenty of GM cars in the
junkyard with this type of wiring. Where the sense wire terminal (Terminal #2) is jumpered to
the output terminal. It does not sense power from the distribution junction
(what is now the Battery terminal on the old regulator) therefore with voltage
drop in the lines it does not get an accurate reading of system voltage.
This is basically a 'one wire' setup.
So now you have an alternator that works. The old voltage regulator
is hanging there, its only purpose to serve as a junction block. Why not
get rid of it?
Go to a junkyard or an auto parts store, and get the distribution block
that is on the firewall
of a GM full size truck. What say '72- whenever. The entire alternator wiring from a S-10 truck works very well, and supplies the wire
from the alternator to the junction block with factory connections. It is perfect. Has
raised walls around it to keep things from hitting it and shorting. I
mount them in front of the battery below the hood prop. Move the
wires there and get rid of the old regulator. It looks stock! They are
extremely ubiquitous, and
One last note of consideration. The internally regulated alternators do not have a bolt hole in the correct location to attach the
support strut that the stock alternators used. Several options are to bend the stock one to fit, make a new one out of sheet metal, or
Note: The following pictures were taken before I put the battery clamp back in.
(c) 2006 Geoffrey A. Johnson
Questions or comments? Email vair1961 (at) yahoo . com
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