I would do it the way Mad says, run a second 10 gauge wire from the alternator to the horn relay, alongside the first.

All the power required by the car is pulled directly from there.

 

Go with MAD Electrical recommendation. I installed their New System kit and I am very happy with it.

 

What is the proper way to do this and keep the car real clean? I do want to get the #150 (Voltage regulator conversion kit) from Powermaster to run my GEN light and stuff like that.

What do you guys suggest or what have you done to keep it real clean.

Thanks, Erik

Since you were using a externlly regulated alternator and now want to use a internally regulated alternator with a working GEN light, you have to convert you harness. I don't know whats included with the powermaster kit, but the one from americanautowire includes everything, and thats the one I recomended since you are already using their harness. You need this one...GM external regulator to GM "SI" series internal regulator
http://www.americanautowire.com/Alternator_Conversion_Kits.html
Since its plug and play (no cutting or splicing required) you could go back to a externally regulated system in the future if you ever wanted to.

or you can just make the connections yourself

8 or 10 gauge wire for 1-3 wire 100 AMP alternator??? I have gotten three different answers from Powermaster, MAD Electrical and American Autowire and I don't know which one to do. Can you help??

Its really a loaded question as every car is different, the reason for different answers. This is one area where bigger doesn't hurt. Using 8g is the safest. If the car is mostly factory and no high current add on accessories, then the 10g is fine. If you have added high currect accessories (like electric fans) use 8g.

Factory fit says I can use the current 10 gauge wire in the new harness and I will be fine. This does go the battery but it stops at the horn buss and the junction block behind the battery too along the way.

Its supposed to as thats the way the factory wired it. Although you have a GEN light, its important to keep it that way if one has a factory amp gauge and want it to work properly.

 

Greg U, in the 12SI wiring diagram above, doesn't the horn buss have a positive post and a negative post. You have two positives coming off each post? Is that right?

The only accessory I run is one 16" Spal fan. Does that still require a 8 gauge wire?

My main question is: Since I have a brand new wiring harness and don't want to cut it up. MAD electrical told me to just run another 10 gauge wire along side the one in the harness to the horn buss. But that still leaves only a 10 gauge doing all the rest of the work to the jucntion block and the battery.

I did order the voltage regulator conversion kit.

Its funny because the guys at powermaster said not to do what MAD electrical does because I will burn my car to the ground someday. I assume thats because he is somewhat competition.

This what I am thinking: I will do the conversion using the american autowire kit for the voltage regualtor and the alt. I will run another 10 gauge wire from the alt back to the positive side of the horn relay along side the original wire.

Does this sound good or scary!!!

Thanks, Erik

 

The horn relay buss has only a positive connection, both screws are +12 volts.

Connect the main power wire for your fan relay to one of the screws on the horn relay.

Run a second wire from the alternator to the horn relay. The 2 10 gauge wires in parallel will be more than adequate. Get some "no stick tape" from a repro house to wrap that short section of harness and no one will ever see the extra wire is there.

If it makes you feel better, you can run a second wire across the rad support to the junction block behind the battery, but I would not, for the following reasons:

Unless you let your battery get REALLY REALLY dead, the existing wire will be adequate for the charge current.

If you are using proper battery cables, the "pigtail" from the positive battery terminal to the junction block is a fusible link. The fusible link will continue to limit the charge current somewhat unless it is "upsized" as well.

If you use a factory ammeter, upsizing the charge wire from the horn relay to the junction block will render the gauge inoperative.

 

Thanks JimM and everyody else who replied!

American Auto wire and Powermaster both sell the Voltage and Alt conversion kits and they look alittle different. The powermaster one actally has another lead off the stud on the alt going into the plug like 2 wires and the Amercian Auto wires plug only has one wire. Not sure what the difference is.

Thats what I will do tonight with the wires. I will run an extra one from the alt to the horn buss. I assumed one was positive and one was negative since they are black and red wires coming off them.

I am by know means an electrically inclined individual, but I always get it done with the help of this site.

Thanks again, Erik

 

and the Amercian Auto wires plug only has one wire. Not sure what the difference is.

The AAW kit for GM external regulator to GM "SI" series internal regulator
has a 2 wire adapter and a small box. The small box plugs into the external regulator plug in the car. All it has inside of it is jumpers. The adapter plug has 2 wires, one is white and hard to see in pic. The AAW kit puts the alternator sense wire at the main splice, just like later models. The Powermaster kit jumpers the sense wire back to the alternator BAT terminal, making it basicly work like a 1 wire alternator with a GEN light.