Hi Everyone,

With the car running I have +11.5V at the battery and ~+35V at the output of the alternator. I have traced all the wiring and everything appears to be connected properly. Any ideas?

Thanks,
Jim

first of all, stop running it like that till you get a new vr. or check the connetors to the vr. and the ground to it.

most likely you vaporized part of the fusable link and it just looks good with no continuity.

had a similar problem, where it got to over 100 volts and vaporized about an inch of 12 gauge line plus 2 inches of insulation, under the dash.

it was due to an intermittent connection to the vr for sensing voltage. bad butt connector.

I didn't know an alt could put out that kind of voltage & it ain't makin sense that the alt is functioning (even at that high rate) but the batt is showing no charge. 2 field terminal alt/flat reg system I'm assuming. As you know either the alt is bad or the reg is or the green wire circuit from alt to reg is grounded which full fields it. You might pull the wire connectors off of the alt male field terminals and ohm the male terminals to ground and you want no continuity and ohm em to them selves & post what you get. With some jumper wires with alligator clips you could pull the present wiring and jump from batt to reg top terminal/either alt field terminal/jump from other alt field terminal to "side" reg nub terminal (the green wire circuit). jump from alt case and reg case to batt neg which'd take the wiring out of the equation & only leave the alt or the reg. I still ain't grasping the high voltage as when an alt is full fielded either for testing purposes or when bad it is 15+ volts. do a visual on the brushes/brush holders. Holler how it turns out.

OK replaced the voltage regulator and it still reads +35V at the post.

Tried reversing the field wires, no change.

Ohmed the field posts and both are open to ground. I ohmed the blue and green wires also and they are open to ground.

It is possible the alternator is bad? I was told it was new and it looks new.

Thanks,
Jim

Yeah, I'm thinking the fusible link is gone as well. Only 11.5V at the battery, even when running.

I have an alternator on order, will try that next. Once I get the output of that under control, then I will check it to the battery.

Thanks,
Jim

double check your vr connections and ground to the body, as well.
make sure there are no breaks, or crimps in the line. or splices that might cause a drop in voltage.

good point.
toasted amp meter?
that would still let you run the car with no charge.
you might check for continuity through that.

I had similar problem and it was the wiring harness connector block at the firewall melted the wire from the alternator into the car. The old cars didn't have heavy need for amperage (radios, etc.), so they thought it was safe to run power from the alternator into the cabin, then through the ammeter and back through the firewall and to the battery. Our cars were rolling fire hazards, particularly if you put in a real stereo or any option that draws power into the cabin. The short term fix is to jump the block with a side wire, or you can bypass the cabin with the charge altogether but you loose your ammeter (but who cares). The modern fix is to change the ammeter for a voltmeter (dash gauge refresh) and bypass the cabin with the high amp charging, just send the wire right to the battery from the alternator. One of the forums had a document with wiring on how to do this. Good luck, can be very frustrating, but the charging system is simple. It's most likely not your alternator if it's putting out that voltage.

Check the volts on the alt output terminal with the eng off. I am betteing its a big fat 0 with the eng off as the only way you can read 35 volts is if the output terminal of the alt sees an open circuit which is most likely a blown fuseable link. The alt output should read 12 volts with the eng off not running and charging volts about 14 eng running if all is good. Ron

What are the voltages at both fields with the car running, and not? What are the voltages at both terminals of the regulator both running and not? The regulator senses voltage at the I terminal, which should be the same as what is at the field terminal with the blue/white trace wire. It then modulates the resistance to ground at the F terminal, causing the field of the alternator to increase when voltage drops, or decrease when the voltage increases above the designed voltage. As you can see from the diagram, the output of the alternator, if it is 35 volts, should be going through the ignition switch, to the terminal on the ballast resistor, and to the I terminal on the regulator. The regulator should be increasing the resistance at the F terminal, lowering the magnetic field created in the alternator, dropping voltage till it reaches around 14.whatever volts. Is there 35 volts at the I terminal when running?

Changing the alternator fixed the problem, but I am still confused.
I was still measuring around +30V at the post, but was getting +13.8V at the battery. When I shut the car off, I was getting 12.5V at the battery.

Amp Meter was about 3/4 way up the positive side, then gradually went back down.

Forgot to mention, this has electronic ignition, not sure if that has anything to do with it.

Anyway, customer is happy!!

Thanks everyone,
Jim