‘67 Belvedere II overcharging

My ‘67 Belvedere II is overcharging, around 15.5 volts. It cooked my last battery. I have a new Deka battery that I don’t want to cook as well.

My car was upgraded to a squareback alternator and later model VR by a previous owner. They also added a HiRev 7500 electronic ignition.

I have tested the Batt. terminal on the alternator with the key off and on and it matches the battery. The blue field wire shows 4.5 volts. The blue wire at the VR shows the same voltage. I checked voltage at the ballast resistor and found that one side had battery voltage, and the other side had the exact same voltage as what I got at the blue field wire on the alternator. It seems that the alternator is being fed voltage through the ballast resistor. The ballast gets so hot, you could burn yourself.

I’m attaching a pic of the wiring. I’m not great at wiring, so I’m looking for guidance on how to figure this out and undo what was done wrong.

Edit - where the brown wire is connected to the ballast is where the lower voltage is. The side to the left with the electrical tape is the battery voltage is.

Start unwrapping wires, and see where they go.The wire that connects to the center terminal on the VR should have battery voltage when the key is on.

R/T Boy 67 said:

Start unwrapping wires, and see where they go.The wire that connects to the center terminal on the VR should have battery voltage when the key is on.

Click to expand...

I forgot to mention that it does not have battery voltage, it has the same 4.5 volts as the ballast.

In a nutshell, the power wire from the ign. switch should feed one side of the ballast, the center pin on the VR, and one field wire on the alternator. All those wires should be connected together. The other field wire connects to the other pin on the VR. The other side of the ballast should connect to the positive side of the coil. The picture below does not show the ballast, but it also connects to the ign wire

Check the center / top pin of the VR. Find out which side of the ballast that wire is connected to. Just do a continuity check with a multimeter you don't have to un wrap everything.

If it's connected to the coil side / then it's sensing the reduced voltage after it goes threw the ballast. And will try to put out as much as it can to reach it's rated voltage.

You want it on the ign 1 side or the side that has full battery voltage when the car is running

So I did a little bit of testing on the harness, but didn’t have a lot of time and wiring confuses the hell out of me, so I ordered a reproduction harness from Evans wiring, but it doesn’t seem right to me. Take a look at these two loose wires. I asked them via email where they go and the response was “They plug in to the headlight connector”. I don’t see where that is. Any ideas? My wiring diagram doesn’t show where these go.

I figured out where those two wires go, but I didn’t end up using the new harness. I found that, in fact, whoever did the wiring connected the blue field wire to the coil side of the ballast, not the 12 v “run” wire. I cut the wires and respliced them correctly and now it charges at 13.75 volts. Also, it idles better, probably because the coil is getting the proper voltage instead of the 4.5 volts it was getting before.

Just wanted to close the loop because I hate open ended troubleshooting threads.