# strange alternator wiring



## MJS69 (Apr 23, 2019)

hi all...got a pic of the wiring on my sons 69 GTO alternator, it seems weird to me...the yellow wire goes to the battery, the red goes to the plug in and then to the electric choke, the black appears to go to the firewall, and the white is just clipped loose...does this seem weird? how should it be normally?

thanks


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## BLK69JUDGE (Jun 10, 2010)

well
I will jump in .......
it looks like you have a 71 n newer alternator bracket ... 69 didnt have that rear bracket...
so
also it looks like its an internal regulated alternator ... also not available on a 69 ...
the clue is the flat plug in and not a square one...
yup 
shes been hacked up .......... probably chopped up at the voltage regulator also

Scott


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## MJS69 (Apr 23, 2019)

thanks for the reply....any thoughts on correcting the wiring or thoughts on why they would have wired it this way?

Mike


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## PontiacJim (Dec 29, 2012)

MJS69 said:


> thanks for the reply....any thoughts on correcting the wiring or thoughts on why they would have wired it this way?
> 
> Mike


Who know why someone would hack the wiring. Maybe that Alt was a freebie and then they got on the internet and read how to hack up the wiring to get it to work.

Your options are to return the Alt/Voltage Reg/Wiring back to stock, or use the Alt with the built in voltage regulator and bypass the factory firewall voltage regulator with a jumper plug kit, or install a late model 1-wire Alt.

It is matter of original vs aftermarket and your skills at wiring.

This should be similar to what you have - Converting a Generator to an Internally Regulated Alternator - Wallace Racing


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## Lemans guy (Oct 14, 2014)

Right and if you are not making a choice to remain original you may want to consider the MAD Electrical wiring kit. Mark Hamilton of MAD is an expert on GM wiring of the era. You can Google some of his stuff and you can call him.

I use his kit and it is awesome, he improves every bit of the factory wiring. Now original is OK and will work, but like PJ said the key decision is original or not.

And MArk is an alternator expert, you can read his papers on line, he knows hot rods and his kits are well worth it.


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## GTO44 (Apr 11, 2016)

White wire should go to the ALT or GEN light on the dash. The red wire is looped back on the back battery post to “self regulate” the alternator.

Simple diagram: https://encrypted-tbn0.gstatic.com/...b0265uIcoKUvncPaK7RB__QZuwe36Q9rUcZnXU5QDGiAQ


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## MJS69 (Apr 23, 2019)

thanks for the replies everybody! goal for the time being is just to have the car running safely and reliably. The voltage regulator on the firewall appears to be bypassed all together, nothing hooked up to it at all. The GEN light does come on when starting the car and then goes off like it should, not sure how it's wired into the system lol. Tested the battery with a multimeter, 14.10 volts when the car is idling, so the alternator appears to be charging....the car has an aftermarket tripack of guages, one of them being alt. volts, not working, can I rUn the white leaf from the alt. to this guage?

thanks again

Mike


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## GTO44 (Apr 11, 2016)

MJS69 said:


> thanks for the replies everybody! goal for the time being is just to have the car running safely and reliably. The voltage regulator on the firewall appears to be bypassed all together, nothing hooked up to it at all. The GEN light does come on when starting the car and then goes off like it should, not sure how it's wired into the system lol. Tested the battery with a multimeter, 14.10 volts when the car is idling, so the alternator appears to be charging....the car has an aftermarket tripack of guages, one of them being alt. volts, not working, can I rUn the white leaf from the alt. to this guage?
> 
> thanks again
> 
> Mike


Not quite sure how the Gen light is working without that white wire hooked up lol. But yes the factory voltage reg is bypassed because of the red wire looping to the back battery post of the alt which puts the alternator in self regulate mode. Clearly the charging system is working if you’re getting 14 volts when the car is running. If you have a regular ‘ole parts store voltage gauge, any 12 volt accessory (Key on) power source will work. Dont use that white for that purpose


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## MJS69 (Apr 23, 2019)

thanks for the reply! lol yeah I have a feeling the wiring is going to be a challenge with this car lol


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## 1968gto421 (Mar 28, 2014)

Lemans guy said:


> Right and if you are not making a choice to remain original you may want to consider the MAD Electrical wiring kit. Mark Hamilton of MAD is an expert on GM wiring of the era. You can Google some of his stuff and you can call him.
> 
> I use his kit and it is awesome, he improves every bit of the factory wiring. Now original is OK and will work, but like PJ said the key decision is original or not.
> 
> And MArk is an alternator expert, you can read his papers on line, he knows hot rods and his kits are well worth it.


Here's MAD's web site: MadElectrical.com - Mad Enterprises

and the electrical section: MadElectrical.com - Electrical Tech

I have used their products---Good stuff and excellent backup/tech advice. If you are not experienced with automotive electrics, I would contact Mark and talk with him, great guy.:smile3:


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## MJS69 (Apr 23, 2019)

thanks for all the great info everybody!?


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## AlaGreyGoat (Jul 6, 2006)

Don't know how it is charging. The clipped white wire is the exciting voltage input from the Alt dash light. Should not charge without a 12V
input on start up.
Here is a diagram for the simple wiring of an GM SI Internal Reg alt:

Larry


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