The voltage fluctuates on my '68, causing a great annoyance and general concern. I still have a "one big red wire to a stud and two little wires into one connector" alternator (generator ?), I assume that also means I have an external voltage regulator.

The dash lights, head lights, electric fuel pump, etc all flutter up and down. It is most prominent immediately after starting the car after it has sat for a few days. After running for a while, and while driving with the RPMs up, it gets a little more stable. However, if I go back to idle, the intensity of the lights will flicker up and down, with the peaks being brighter than the equilibrium brightness. I haven't had a chance to catch it with my volt meter. The battery terminals are clean and I have a good ground.

What is the mode of failure on the voltage regulator? Does it allow fluctuations like I am discribing? If it is dying, is it time to put on a "one wire" alternator? What do you have to do to the wiring to do that?

Thanks for the opinions!

I'd replace the voltage regulator, at least. They're relatively cheap, but...I've found that there's a big variation in quality. I've had my car since 87, and the first time the regulator went bad about 4 years ago, I went through 3 of them within a month till I got one that lasted...which is still going strong, by the way. I can't speak to the "failure mode" of the external regulators, but I do remember that my original did have severe fluctuations, but I can't really say if it only did that right before it failed, or if it always did that. One wire alternators are nice, but I really don't see a huge advantage in having one.

As a side note, I think that the comment above about the great variation in quality pertains to a lot of the parts counter stuff you get at places like Pep Boys, Advanced Auto, NAPA, Big A, A1, or wherever. A lot of it is just junk...espcecially rebuilt items like brake master cylinders, brake calipers, alternators, starters, etc. It's like Russian Roulette, you buy it and hope it doesn't go off. When something fails, I find it's not uncommon to go through 2 or 3 replacements till you find something that works. Like what I went through with the voltage regulator, I had the same problem going through 3 alternators, 2 master cylinders, 2 starters, all at one shot apiece, just to get one that finally did the job.

The advantage to a one wire alternator is no troublesome regulator.Electronic reg built in...FRED

These older type regulators do use mechanical contacts to adjust the voltage. If the contacts get crudded up the voltage will vary until it burns the contacts up. One thing to consider with the internal alternators is that they are pretty high output starting at 60+ amps, your old one is maybe a 37 amp job. Rebuilt internal for about 45 bucks around here. tom