New wiring harness problem. Need help!

[jcspaek009]

So I just rebuilt my 400sbc in my 72' c10 and also put in a new painless wiring kit, I fallowed the wiring instructions to a "T" also looking at the old (original) harness for a reference when needed. I put a new Alternator in as well, so I fired the truck up a couple days ago and it started and ran no problem until i tried to shut the truck off when the Alternator started to smoke a little and got very hot, the truck wouldn't shut off so I had to pull the coil wire to shut it down, I called painless and they said this does happen sometimes where the vehicle won't shut off and that I needed to install a diode on the excitor wire (white) to fix it, so I put the diode in and it still won't shut down and the same alternator smokes and gets very hot, also I don't have a ballast resistor and it didn't have one when I got the truck. Any help would be great cuz I'm loosing my mind and just want to drive the truck now that the snow is gone.
Thanx

[jcspaek009]

Also forgot to say since I didn't have a ballast resistor I just took the "pink" coil wire that's off the fuse panel right to the coil,

[airdale94]

Did you get the diode installed the right direction. VetteVet is the one you need to talk to. He's the guru when it comes to charging system wiring. He's got several custom diagrams on other posts. You can search for his posts or alternator/charging system problems, or might try PMing him. Tell him how much you like Corvettes and the (United States) Air Force.Do you still have your external voltage regulator? Is your new alternator internally regulated?

[Motoxrrar]

I think painless will send you the ballast resister for free. They sent me one.

[jcspaek009]

Thanx for the reply guys, yes I have the doide in the way buddy from painless told me (the strip/marking towards the alternator) The truck didn't have an external regulator when I was taking the old wiring out and I believe my new alternator is internally regulated like the one that was in the truck,
I'm wondering if I got it working but because I was trying to use the new alternator that I smoked and it got really hot that it might have got fried the first time and now it is toast, and of course I can't find my receipt for it to take it back.

[airdale94]

You only need the ballast resistor if your running a points distributor. If you are, the reason you diddn't have one before is it's built into the wire that goes to the coil.

[burnin oil]

I would unhook the alt and see if everything behaves. The internal alt has the wiring plug on the side instead of the back of the alternator. The plug should be a rectangle instead of the rear mounted square. The wiring plug is what controls the alt turning on and the output with the large wire on the rear controlling nothing. It is just the output lead that goes to the battery. If everything works normally with the plug off then you know it is the charging circuit. If the problem persists it is an issue with the new wiring. It could be a faulty ignition switch keeping power going to the ignition or a crossed wire somewhere or the ignition is picking up power from an always hot circuit. With new wiring you have to double check everything.

The ballast resistor is not needed as said before due to a resistance wire in the harness, atleasst the stock harness. Either way the ballast resistor is not needed. Its purpose is to lower voltage to the points during normal operation to increase their service life. During start up they get the full 12v from the wire going to the starter solenoid and around 9v during normal run.

[VetteVet]

Your problems sounds like a classic mistake of having the two wires in the alternator plug reversed. This might be because of the new harness or it could be because of the regulator wiring being crossed.

If the wires are reversed the engine may not shut off because of alternator feedback to the ignition switch and or not having a resistance in the charging wire. You are calling it a white wire which is was in the original harness. There has been some confusion as to what wires to jump in the original harness external regulator plug, which you may not have with the new harness.

If you do then you need to find the brown wire that comes out of the firewall connector by the master cylinder, which runs to the external regulator on the "F" terminal. It will be on the end of the plug. This wire will jump to the white wire and continue to the alternator and will connect to the no. 1 terminal on the alternator. The other two wires that jump on the plug are the red wire at terminal 2 on the EVR and the blue wire at terminal "4" on the EVR.


Here is the correct way to jump the EVR plug wires.





The result of having the wires reversed, is that the alternator will excite and charge, but it will not regulate the amount of voltage and current output because it cannot read the system voltage so it defaults to full output. This will cause it to overheat and overcharge the battery and possibly blow some lights. The diagram shows how the wires could be reversed. The correct way is brown to white and red to blue. Then at the alternator it will be white to no.1 and blue to no. 2.

I usually eliminate the jumpered wiring and run the brown wire directly to the alternator at no.1 and then run the red wire to no.2 as per the diagram below.



Some guys just loop a small wire from the large wire on the alternator over to the no. 2 terminal. This is the sensing wire for the system circuit and it activates the voltage regulator inside the alternator. This connection works, but it is not as efficient as the previous method, because it does not sense the voltage drop downstream from the alternator, so it does not compensate for that.


The blue wire will continue to the alternator and connect to terminal "2" on the alternator.

This is the conversion for the internal regulated SI series alternator, if you have the original alternator or the newer CS alternator then there are differences to the conversion.

We have to know what alternator you have for sure and what harness you have installed. Is it original or modified?
It will be helpful to know what dash cluster you have Gauges or Idiot lights.

Either one of these dashes should have a resistance in the wiring to the external voltage regulator brown wire,so no diode should be needed. The diode will prevent feedback voltage to the ignition switch and it does have some resistance so it works too.

Here is another diagram showing how to wire the alternator.





Check out what I have posted and get back with the results. VV

[airdale94]

I told you VV would be the one to talk to!