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Discussion Starter #1
I just installed a 140 amp internally regulated alternator in my 1968 along with a Mark VIII fan. The alternator came with no instructions.
I hooked a 4 gauge wire from the +BAT post on the alternator to the battery.
My question is this:
Where do the other three wires from the alternator go?
There is a ten gauge wire that used to hook up to the alternator, but I am assuming that with that gauge the alternator would melt the wire. I'm also assuming that this 10 gauge wire is responsible for everything from tail lights to warning lights to providing me with power for my ignition coil. Where should I hook this up? Can I just put it behind the +BAT on the alternator? Do I need something to drop the amperage?
What do I do with the old voltage regulators?

Premium Member
4,060 Posts
The first step is finding the correct alt. for your application. There are two types of internally regulated alt. by GM. They are the SI series and the CS series. The SI series are typically found on cars of the 1970s and early 1980s and usually have a single groove pulley (V-belt driven.)

The CS series are found on later, fuel injected or ECM type cars and usually have a multi-goove pulley(serpentine belt driven.)
you Dont need anything to drop the amperage.
amperage=current and if your accesories dont require that much amps then the alternator will only supply what is needed.

You are more likely to find an SI than a CS unit. The SI can be found remanufactured or at a salvage yard. Parts are cheap and readily available. The unit is rebuildable in the field. The CS unit is quite expensive and not rebuildable.

There are two types of SI alternators, 10-SI and 12-SI. The 10 has a 63 amp output and the 12 is 94. If your car is basically stock, the 10 will do fine. If you have a lot of power accessories, high perf. ignition, lots of gages etc., you will need a 12. There are upgrade kit availble by Quick Start which boosts the alternator output. Kits include new stator ring and diode trio. Kits are available from parts sources such as Summit Racing. If you require more output, the CS alternators are 105 amps but require pulley changes and wiring upgrades to handle the increased amperage.

The 10 and 12 can be differentiated by the cooling fins on the alt. rear. The 12 has six large cooling vents while the 10 has three smaller vents. The mounting holes and wiring is identical.

After you have found the alt., make sure yo get the wiring connectors, plastic two wire connector. These are availble at parts stores if you can not use the spade connectors of the right size. Make sure the alternator is visually okay, no excessive play on the pulley shaft, no signs of damage, stripped threads etc.

The wiring is quite simple and makes use of the wires already in place. The external voltage reg. is removed entirely from the circuit. You are then left with 4 wires originally connected to the volt reg. F,2,3,4 (note which is which with a marker or tape.) Do the following:

1. Cut the connectors off each wire, no longer needed.
2. White wire (2) is no longer needed. Other end at alt.
3. Red wire (3) can be taped.
4. Blue wire (F) and dark brown (4) should be soldered or
spliced together. This is the exciter to turn the alt. on.
This completes the removal of the old alt. and ext. regulator. Now, let s wire the new high output alt. There are three connections: two male spade connectors with a matching female and ring post located on the rear. The two spade connectors are marked 1 and 2. If unknown, face the rear of the unit, the left one is 1 and the right is 2. Now, do the following:

1. Solder/splice the blue wire to 1.

2. Use a 14 gage or larger(numerically smaller) wire to go from 2
to the BAT ring post on the rear.

3. Attach the orig. red charging wire to the BAT also. Ensure this
wire leads to the battery as this does the charging.
Mount the alt. The belt size will be the same as the old one. Start the car and read the voltmeter which should be 12-14 volts. If no voltmeter, use a multimeter to read the voltage across the battery terminals which should be 13.9-14.8. Do this test at a high enough rpm, 1600, to turn on the alt. Alt. should now be able to support all power accessories. If not, you need a higher output alt.

Premium Member
22,122 Posts
I second the conversion harness. There's 2 peices, one converts from the alternator plug in the car to the one on the new alternator, the other one plugs in in place of the old voltage regulator.

Also, if you search a bit here, there was something within the past 2 weeks with a link to everything Dawg said correctly above, BUT WITH PICTURES and wiring diagrams!!
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