You guys have probably seen these questions a thousand times, because I've been looking for hours at some of the old posts...Lately my Alt gauge needle has been jumping around, sometimes the flicker slows down or speeds up based on rpm. Today I left on a 60 mile trip and it stayed steady the whole way at about a -15. Then when I started back this afternoon it pegged at +40 and stayed that way for 50 miles, eventually dropping a little bit to about +30..
Does this inconsistency sound more like regulator issues or the dreaded bulkhead connector/amp gauge issues? thanks...

You cannot troubleshoot by guessing, or asking for guesses. I'm not trying to down ya, I'm just sayin.

You actually have to get in there and check things.

This could be something as simple as worn--out brushes, or a filthy greasy slip ring, etc

And it could be a lot of things, as you mentioned.

First thing I'd do is get it at a good fast idle, simulate low to medium cruise, and get someone to realy eyeball the ammeter. Then wiggle the regulator connector, the bulkhead area, and reach up under the dash and wiggle the ammeter wires, and feel for hot wiring.

If that doesn't lead anywhere, eliminate the regulator circuit. Get two good clip leads, and unhook both push-on connectors at the alternator.

Clip one lead on the alternator "bat" stud, the other end on one of the exposed push-on terminals

Clip the other lead to ground, and the other end to the remaining exposed alternator terminal.

Now start the car and gently increase engine spead, watching the ammeter. You will be "full fielding" the alternator, so don't overdo it. The more RPM, the higher the amp reading. What you are watching for is to see if it's STEADY and not jumping around.

If it's steady, turn on the headlights, and if it stays steady, add the heater blower. If it still stays steady, then the problem is likely in the regulator circuit.

If not, could be the brushes/ related, wiring starting at the batt output stud on the alternator, all the way two and onward through the bulkhead to the ammeter, and back through the bulkhead to the battery.

If it's jumpy, check all this carefully. Pull the bulkhead connector loose and inspect, look for loose/ corroded/ deformed contacts and melted wiring.


If the above test showed steady, then it's probably in the regulator circuit. Check the regulator ground, the ign supply to the regulator (comes through the bulkhead) and the green wire from the regulator to the field.

Also check the blue wire going to the alternator field--this comes from the ign switch, through the bulkhead, to the ignition, the electric choke if used, and the alternator field


Frankly it's very difficult to troubleshoot these prolems "by remote control"

The alternator is new, only a few months old. And that was what is weird about the symptons- Last few times I've driven it it was the jumpy needle, but staying mostly on the positive side...today it was dead steady needle, just negative all the way to work, then pegged in the positive all the way back....I'll start checking things this weekend, maybe look at my parts car first to get an idea of where all the connections are..

First thing I would check is the connections on the amp meter. You should be able to get to them from under the dash.