Changing your 6 volt vehicle to 12 volts by
Al at AutoReWire.com
Converting from 6 volts to 12 volts is pretty
I get a lot of emails regarding this subject.
What I have done here is to provide you with a sort of
road map to perform the conversion. Obviously
you will need a few parts and some supplies. I
have included links to the products that we normally
keep in stock and have included links to others that
supply products we don't stock.
your wires are in good condition they will handle the
12 volts just fine as they are twice as heavy as they
need to be. The same is true of the switches in
Remove the old Battery
and DO NOT INSTALL THE NEW ONE UNTIL YOUR DONE.
GENERATOR If you are
keeping a generator you will need to replace both the
generator and the voltage regulator with units for a
'55 or later 12 volt model.
If you are replacing the generator with an alternator
I would suggest that you Google "
replace generator with alternator
" for a better understanding of what is
involved. I will outline below the most popular
GM 10/12 SI alternator conversion. I have also
supplied links to Mark Hamilton's site as he does a
great job of describing the reason
for using a 3 wire instead of the popular 1 wire
alternator. Other alternators will
install similar to the GM. More information is
available on the web via your favorite search engine.
GM 10 or 12 SI ALTERNATOR -
Most Popular Conversion
Remove the generator, voltage regulator and the
wiring between the two. Mount a GM 10si
or 12si alternator in place of the generator.
Universal brackets are available at most local Napa
auto parts stores. On most vehicles you can
simply cut the appropriate lengths of 3/8" black iron
pipe to make the spacers you need to install and align the
alternator. You may have to change pulleys if
you have an older engine that uses a wide V belt (more
For information on part numbers and case clocking go here.
You will need to open up the wiring harness to do this
if you haven't already. We have 3/4", 1" and
1-1/4" Non Adhesive Harness Tape available to properly
re-wrap the harness here.
Splice a 10 gauge wire onto the BAT wire that went to
the voltage regulator and connect it to the BAT
terminal on the GM alternator. Don't go to the
trouble of buying a 1 wire alternator unless you just
want to get a chrome unit. The factory 3
wire units will last longer and charge better. For more info on this subject go here.
If you are using an ammeter in the dash DO NOT use an
alternator larger than 63 amps and MAKE SURE that you
install a 4 inch (minimum) length of 16 gauge
fusible link between the alternator and the ammeter so
that the gauge does not become the fuse in the
circuit. I like to install the fusible link at
the alternator to keep it out of the passenger
compartment and for ease of service if it should ever
fail. We have the Fusible Link Kits available.
If you have a dash indicator light splice a length of
20 or 18 gauge wire
between the wire that went to the ARM on the voltage
regulator and connect it to the # 1 terminal on the
alternator. Go here for a drawing.
If you DO NOT have a dash light you will need to
run a 20 or 18 gauge wire from the IGN switch to the #
1 terminal on the alternator and install a 10 Ohm 10
Watt resistor somewhere in that line in a place where
it has good air circulation.
It is best to run at least 36 inches of 12 gauge wire
from the #2 terminal on the alternator to the BAT
connector on the starter solenoid (or the fuse panel
or the horn relay) as apposed to just jumping it as
shown in my drawing. If you read the Mark
Hamilton article you will know why.
Another tip on Fusible Links.
GM designed the systems with the sensing splice in the
harness and the 10 gauge system supply wire has a
fusible link at the starter solenoid. If you run
the sensing wire to the starter solenoid you are smart
to install a fusible link in it AND in the BAT charge
wire. The ROT(rule
of thumb) is to use a fusible link that is four sizes
smaller than the wire you are protecting. So if
you using a 10 gauge wire from the alternator to the
starter solenoid then you would use a 4 to 6 inch
length of 16 gauge fusible link.
STARTER... Your existing 6 volt starter will
work just fine for a long time if you do not crank it
for long periods of time. Of course cranking any
starter for long periods will burn 'em up (as in throwing solder
due to over heating) but the 12 volt driven 6 volt
starter will get hot quicker and throw solder sooner
that a 12 volt unit Replace the starter
solenoid with a 12 volt unit for a '55 or later
model. I have the early Ford style in stock
for $ 10.00.
COIL... You can use the original coil but you must
install a new ballast resistor (1.2 to 1.8 Ohms)
between the coil and the ignition switch. I
always test the coil output when I convert a car for a
customer but it requires a special tester that most
people don't have. Anything over 30,000 volts is
sufficient for a non performance engine. You
will need to reverse the polarity of the coil if your
6 volt systems was
Positive ground as most were. Wiring should run
from IGN switch to one end of the ceramic resistor
then from the other end of the resistor to the + post
on the coil then from - post on coil to the
points. Points and condenser can be
retained if they are in good condition. If you
need a new condenser, one for any 12 volt vehicle '55
or later that fits in the distributor will work.
HORN RELAY... Replace the horn relay with a 12 volt
unit. Most 6 volt horns will work for a
very long time on 12 volts, eventually you might need
to change them to 12 volt units. Some fan fair
horns have an adjustment knob on the disc that you can
adjust the tone with. I wear ear protection when
doing this, you should too. We have some good USA
manufactured units for $ 30.00 a pair... They
are plentiful at the local pull your own part wrecking
LIGHTS... Replace the headlamps and all of the light
bulbs with new 12 volt units. Yes this means you
have to replace the ones in the dash that are
sometimes very difficult to get to.
GAUGES... Install one of our $3.00 (each) voltage
reducers for each of your electrical dash
gauges. Not needed for the Ammeter.
HEATER ... Install a 1 Ohm ceramic
reducer between the heater switch and the
heater blower motor. $
WIPERS... If you have electric wipers you will need to
install a 1.5 Ohm ceramic
reducer between the switch and the motor.
$ 22.00 each.
TURN SIGNALS... Change turn signal flasher to a
12 volt unit.
POWER SEAT and CONVERTIBLE TOP MOTORS... Most
will work fine with a 1 Ohm Ceramic Resistor others
will need a pair of 1.5 Ohm Ceramic Resistors wired
parallel to produce .75 Ohms. Best way to test
for what you need its to
install a 1 Ohm and then check the voltage at the
motor with it running. It should be between 6.5
- 7.5 volts although something less will work without
damage. If the voltage is below 6 volts you
might need to go to two 1.5 ohm resistors.
RADIO... As for the radio, the best bet is to go to Custom
Auto Sound and get a unit that will
replace your original.
You could also have your 6 volt radio rebuilt to work
on 12 volts. Do a Google search on "Antique Auto Radio" for
more information. For the D.I.Y. who wants to
"try" and make it work read this and this.
CLOCK... It is best to have a new quartz
movement installed. Do a Google Search on "Automotive
Quartz Conversion" for more info.
To purchase any of the above products please visit our
or our Ebay Store. If you
can't find them in our stores we are temporarily out
of stock. You can call me at 209-481-6496
anytime 8am to 8pm Pacific time
to order with a credit card or send me an email with
your needs and I can send you a Paypal
or Google Checkout invoice. International
shipping is available.
and all comments are welcome. If you feel
something should be added please let me know.