Voltage steady when drawing on battery, but jumpy when on Alt..why?

I am still in voltage jumpy hell. Now wife is making fun of the pulsing lights on our 66 dart with the HEI and elctronic voltage reg. I won't list the numerous things I have tried, so this question is more of an "enlighten" me moment.

Why is it that if I load up the electrical system enough so that the battery kicks in, at that point the voltage is dead stable, with no pulsation at all, solid. But as soon as load is lightened and the battery no longer needs to help, then my voltage gets jumpy and lights begin to pulse.

Short answer ( not very technical) is the battery is dampening out the electrical pulses your charging system is putting out. Under light load the battery is at a charge state where it doesn't do that.

I don't know. I have a question though... Is yours a round back ( OEM type ) or a square back higher output alternator?

RedFish said:

I don't know. I have a question though... Is yours a round back ( OEM type ) or a square back higher output alternator?

Click to expand...

Yes well I have my original Roundback, then tried 4 different newly remanu round backs, then tried a reman square back (grounded one terminal), and now I am using an NOS chrysler 70's squareback with one terminal grounded (70amp)

I experienced the same issue with all of these alternators.

I can't draw from my own experience here because I don't have it. Every time I've upgraded to a isolated field alternator I have added the 1 wire needed to isolate the field, along with that more complex voltage regulator. The higher educated engineers did that for a reason ( better control the field current / charging system operation ). I don't pretend to be smarter than those engineers.
So... 10 thousand posts on this interweb state, "just ground 1 field terminal ( retains the closed field circuitry ) and it will work just fine". Does that apply to all of the millions of various examples? Maybe. I'll never know if it applied to mine.
There is documented proof that the corporate bean counters omitted 2 of #158 bulbs from a certain Dart instrument panel for a time, to lower cost. That tells me they would not have added a 2nd approx' 5 ft. length of wire from the alternators field back to the regulator if it wasn't necessary.
In the end, Just sharing what little I do know. Good luck with it.

Here's a link to a thread I started. This is how I fixed mine.
Good Luck

Lights flicker and gauge jumps around???

Ok short update, will know more tonight when I can turn on the lights.
But I swapped out the new vr, with that Blue one everyone talks about. You know the one that says it is for racing. I scraped off the blue coating, and swapped it in. Started up and voltage is now pretty stable at 14.0. This is lower than the other VR I had (which was jumpy from 14.5 - 15). I tried to load the BLue one up, fan, brights, radio and it got me to 13.5. So I am hoping that tonight when I hit the lights, they will be steady. finger crossed.

The reason they do that is because the terminal of the regulator that senses the system voltage is not getting the real reading, so the regulator pulses.