be the Judge!
most applications, the advantages of a THREE-WIRE
alternator will far outweigh the little time saved
with a ONE-WIRE installation.
types have the voltage regulator in the alternator, but
there are important differences between the ONE-WIRE and
Enterprises does not sell alternators, and we never have.
Therefore we have no reason to slant this story.
advantage of the THREE-WIRE system over the ONE-WIRE
system is exactly why we made our part#ALT-1, alternator
wiring kit, beginning back in 1989.
(Rather than simply sell ONE-WIRE
alternators–which would have been very easy for us to
THREE-WIRE advantages are even more important in recent
years–More powerful alternators are often installed on
Hot Rods and they must support a more power hungry
note, from author
Mark Hamilton, M.A.D. Enterprises
is a fairly involved topic, and this feature contains
issues that have never before been directed at the High
Performance automotive industry.
It was posted for the enjoyment of those who enjoy
learning how things work.
those would like the advantages of the THREE-WIRE without
caring much about how it works, our part # ALT-1,
alternator wiring kit has pleased thousands of people in
the years we have sold it.
The kit makes it simple to wire the THREE-WIRE
system without knowing why or how the system works, and we
have kept the price tag low for the kit too ($27.95).
who would like to check the performance of an existing
system, ONE-WIRE or other, can get out the voltmeter and
see how well the system is working.
Check voltage at various places.
Like with engine running at cruise RPM, headlights
ON (high beam), heater fan on medium blower fan speed,
measure the voltage at a brake light or dome light fuse.
That measurement will indicate voltage from the
dash area “main power-up wire,” which is a very
indicator of overall performance.
(The dash area “main power-up” supports
ignition, lighting, and accessories.)
we think performance is pretty good, but we never know how
good performance really could be until we test it or
compare it to something better.
It’s surprising how much stronger HEI system
(ignition) is at 14 volts, compared to operating at 11 or
12 volts. And
the same is true with the headlights, the strength of
electric radiator fans, and other items.
in this feature applies to all alternator systems, not
just the 10SI and 12SI Delco systems.
real story STARTS here!
the facts, please…
operate a Warning Light
read “Voltage Sensing”
from alternator? (2)
at nearly all
Parts Stores? (3)
knowledge required for
Even with a VOLT gauge at the dash, it’s a good
idea to also have an alternator Warning Light. (We can have both.) Warning
Lights are easily added at custom dash panels and at dash
panels that did not come with an alternator Warning Light. Warning Lights attract attention immediately.
With only a gauge at the dash it’s easy enough to
be in real trouble before an unusual reading is noticed.
The best is to use a Warning Light and a gauge.
the Warning Light comes ON while driving, watch the
Water Temp gauge!
The belt may have tossed or there may be other
problems, which have stopped turning the water pump.
the ignition is switched ON without the engine running
(for service work or for any other reason) the warning
light is a good reminder that the ignition is ON.
Voltage-sensing” is a must for good electrical system
performance with most factory-original type wire harness
have explained the Remote Voltage-Sensing function in our
Tech Section, where a feature essay is dedicated to this
because knowledge of remote voltage-sensing is important
to this comparison, here’s a brief explanation.
alternator is the source of power used to operate the
ignition system, lighting, and other electrical system
the parts will deliver best performance when operating
at about 14 volts.
The voltage regulator will always attempt to
maintain the electrical system voltage at about 14
the original wire harness will feed power to these
parts from a “main junction” in the wiring,
which is often far downstream from the alternator.
The voltage regulator can maintain 14 volts at
the “remote main junction,” if we give the
regulator opportunity to read “voltage-sensing”
from the junction.
ONE-WIRE, without REMOTE VOLTAGE-SENSING option,
as an “intended up-grade” from a 55Amp
externally regulated to a 100Amp ONE-WIRE can
result with dim lights, weak ignition, and weak
performance in general.
(Especially so when a factory-original”
type wire harness system is used.)
And at M.A.D. we have received many phone
calls from people who have experienced the result
of such conversions.
models are the most readily available, because for many
years they were factory installed on nearly all makes and
models of GM cars and pick-up trucks.
POPULARITY as a
replacement service part and also with retrofit up-grades
has made the THREE-WIRE 10SI and 12SI models the least
expensive alternator/regulator system in the industry.
The ONE-WIRE system
was designed and intended for limited applications,
because not much knowledge is required for installation
This is the only significant advantage of the
ONE-WIRE, and it is a major advantage that has
contributed much enjoyment to the sport of Hot Rodding.
At least, the ONE-WIRE has provided a simple means
of charging and maintaining the battery while driving.
This is an important area that might have been
troublesome for a lot of people, if not for the ONE-WIRE.
(And therefore this “tech feature” is in no way
an attempt to “bash” the ONE-WIRE alternator system.)
12SI Delco alternator is a very good up-grade for many
makes and models. We
have all seen them used as an up-grade on Chevy and other
GM cars. Here’s
one that has performed very well on a FORD, for many years
and lots of miles. At
the time of this writing it still serves as a daily
driver. Often this alternator has had to work hard, and
sometimes for long days.
There are four electric radiator fans (all come ON
at once), another fan on a transmission oil cooler
(foreground), a powerful air conditioning system, a small
sound system, electronic ignition, Halogen Headlights on
relays, and there are two batteries that must be
a stock, DELCO, THREE-WIRE alternator, and was wired using
M.A.D.’s part #ALT-1 kit.
The system also operates the factory “GEN”
warning light at the dash at this ’64 FORD.
FORD (shown in previous photo) is a ’64, which came with
a generator, not an alternator.
It’s a nice touch to make use of the original
Warning Light at the dash, when using a stock dash system.
And this GEN light works perfectly with the
THREE-WIRE 12SI, wired using M.A.D.’s part # ALT-1
alternator wiring kit.
(Shown with Ignition Switch ON, engine stopped.)
The THREE-WIRE system will also support the factory
“ALT Warning Light” when converting from the
externally regulated alternator systems.
many years the model 10SI and 12SI DELCO alternator has
been a favorite for all types of cars, trucks and
Here’s a THREE-WIRE 12SI on a ’30 Model A FORD,
and it still has a Model A engine!
(The old Model A generator was not strong enough to
support ordinary sealed-beam headlights, the Model A had
small light bulbs in a large reflector lamp assembly.)
Notice that the old Model A has also been up-graded
to electric radiator fans, which save horsepower when
cruising (especially when revved up to 45 MPH!)
Ha! (The fans are not needed at cruise speed, and
it really does save horsepower not to pull a fan on the
the dash of the old Model A, the 15 AMP gauge was removed
in favor of a Warning Light, which operates perfectly with
the THREE-WIRE model 12SI alternator.
(Shown with ignition ON, engine stopped.)
here to continue to Part 2