Jumping guage & pulsing lights

[OUTLAW]

Here is one I thought would be a simple fix. When running my volt guage will jump back and forth between 12 & 14 volts then steady and do it again continuously. Also with the lights on you can see them pulse up and down (headlights and dash lites both) .Thinking it was a brush bouncing in the alt or a diode failing I replaced the alt and voltage reg with new ones ( a total of 3 each) and it still does it. I have gone through the whole car checking and cleaning grounds and adding several extra grounds , and I have replaced the volt guage on the off chance it was bad. It keeps the battery up ok but just bugs the hell out of me. Also I have hooked up my Snap-on analog volt meter directly to the alt and it is steady. I assume it has some kind of damping built into it. Any ideas I missed?
thanks

EDIT: This is the old single field alt and mechanical voltage regulator if that helps

 

[67Dart273]

The most likely cause of this, since you already looked at the brushes is a bad mechanical regulator. I'm assuming you have the older 69/ older mechanical regulator?

(Look under the regulator. IF there's two large resistors under there, its a relay type.)

But BEFORE you replace it, make a test:

Turn the key to "run" with engine not running. Set your meter to low DC volts, and stick one probe on the regulator IGN terminal (the push--on terminal) and the other probe on the battery POS post, or on the starer relay stud

You are hoping for a very low reading, the lower the better. If you have more than .3V (three tenths of one volt) you have a voltage drop problem.

The circuit path envolved is from the battery -- fuse link -- bulkhead connector -- ammeter circuit -- in harness splice -- ignition switch connector -- through the switch -- back out the switch connector (on the dark blue "ignition run" [IGN 1] wire) -- back out the bulkhead connector -- and to the ignition system and regulator IGN terminal.

Your top suspects are the bulkhead connector, the ignition switch connector, the switch, and in rare cases, the ammeter and it's connections, and more rare, a faulty "in harness splice." This is a welded, factory splice in the black ammeter wire, which feeds off to the headlight switch, ignition switch, and a few other things.

If this checks out OK replace the regulator but PLEASE buy yourself a GOOD one, and they are EXPENSIVE

NAPA/ Echlin VR1001 or Standard VR 128 is what you want.

Please do NOT buy "no name" or "Wells" branded regulators.

While you are at this, you would do well to unhook the connectors at the bulkhead, inspect them carefully and repair as necessary. Most of these old girls seem to be having problems in this area. Even if you don't perform "the bypass" this excellent article gives you an overview of the "whys" of these problems:

http://www.madelectrical.com/electricaltech/amp-gauges.shtml

 

[OUTLAW]

This car doesn't have a ammeter guage in it it uses a volt guage. But I have to assume 3 new ones would rule out the v-reg. I agree ...spend the money on quality parts and leave the white box parts for the chevy and fords

I totally re wired the car a year ago and replaced the bulk head connector with a high end weather -tite box I made and that was the first place I went just in case

 

[67Dart273]

Somehow I missed your post "snap on voltmeter"

So what's between your snap on and the in-car voltmeter?

Is the battery up front or in trunk?

 

[BillGrissom]

You haven't answered 273's question about what type of Vreg you have. Pulsation is normal for a mechanical Vreg (60's cars) since they control the alternator field as on/off.

I am guessing the voltmeter is not factory for your car since most had an ammeter in the dash. No idea why 2 voltmeters would disagree, but as 273 says, you aren't probing the same points. As you guess, one may have more damping, but sounds like your on/off is on the order of 5 sec which is a lot of damping.

We can't do much if you don't let us know the year and model of car and all the electrical changes made to the factory design.

 

[RedFish]

I had the same fault condition. The volt gauge pointer would twitch very fast at times.
The later model solid state regulator was the problem. New one fixed it.
as stated before, buy a quality replacement.
Always properly mount/ground a regulator before supplying power to it.
Good luck