To catch you up on what I've done so far here's the story.

My wife's 65 valiant was running and charging great. Alternator died about 6 months ago, replaced alternator and regulator from Oreally's (they had parts in stock). One day about a month ago it stopped charging. Still ran great no issues. Checked the alt, tested fine. Changed the VR with NAPA part, low and behold she's charging again! Once the battery was charged (charged at 2 amps with my household charger til full) I noticed the ammeter jumping and the dome light surging bright and dim. Scratched my head a bit, and tore into the wiring. Fusible link had the insulation melted away (looked like it was that way for quite some time) so I replaced it. Checked wiring behind dash, reseated all terminals on back of cluster and made sure everything on the circuit board were making good contact, put it together and still the surging continues. Checked firewall connections, not much corrosion there looks well preserved, but brushed and greased the contacts anyway. No change. The ignition wire (yellow going to ballast and to coil) has a butt connector from previous owner. Looks like the power wire going to the coil got grounded and burned up a bit, but resistance is negligible from ignition switch connector to firewall to coil. Not part of the charging circuit but though it worth mentioning. Checked voltage at field on regulator - 8.5v? Spade terminal at regulator seemed more realistic at 14.7ish volts, but the voltage dropped randomly. Hard to say how much my digital reader has a delay, and on my analog battery tester it would drop to about 3V before jumping back up to 15ish. Checked grounds from batt to block and block to firewall, a little corrosion at block. Replaced negative cable to block and added (for my sanity) a ground wire going straight to regulator, still no change. Bypassed the gauge on the dash (put alternator wire directly on fusible link connection) and voltage was surging from 14 to 17 volts at the battery (previous tests at battery showed 15.5v consistently at battery). Took alternator to oreallys and swapped it out for a fresh reman, and this is where it gets interesting. Initial fire up gave me a few surges at battery, then voltage dropped to 12.5V at idle. revving to 2500 RPM voltage slowly raised to 15.5V at battery, and when I let it idle again, voltage dropped to 12.5V again, but voltage surging is gone! I know this is long winded but bear with me.

So question 1: does the regulator on the back of the dash have any connection to the regulator? (I have a few spare dashes that I can swap the regulators from when I have more time)
Question 2: More of a statement, but I think the reman alternator is to blame, but I'll have to wait a few days for them to restock another. Or should I ditch the ultimas for a better alternator?
Question 3: What could be the source of the weird voltage drop? And could it be the root of my problem or something else entirely?

I'm about to my wits end with this problem. Any input is appreciated. I may be overlooking something but cant imagine what!

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65 Valiant 4 door 3 on the tree 225 /6
65 Valiant 2 door Auto 225 /6

1: no
2: don't think it's the alternator
3: my guess is the alternators regulator

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Dash voltage limiter that powers fuel & temp gauge would have no effect on main harness voltage fluctuation. That said, main harness voltage surge could cook both mentioned gauges if limiter can't handle continuous high voltage.

I think the voltage regulator is the problem, where you have already removed any voltage drop in its ground path.

For a test with engine off, disconnect top blue wire to voltage regulator, and run a temporary jumper between VR's top terminal to positive 1/4" stud on starter relay which electrically is same as positive battery terminal. Start engine; this test eliminates all the likely voltage drop suspects that blue wire you disconnected would feed to the regulator. See if the system levels out to between 13.8 to 14.2 volts. If not, kill engine, then run a 10 Gauge jumper between output stud on alternator and positive battery while leaving first jumper in place. Start engine; if that fixes the problem, than you need to find where the voltage drop is in harness and eliminate the drop by cleaning or replacing any brass connectors and or any bad conductors, and or switches. Don't forget to check all the taped up factory soldered splices under dash along both the black and red #10 main power conductors running between battery through fire wall to amp gauge and back out to alternator. If one of those are bad that could cause an intermittent high resistant connection and goofy voltage level reading by voltage regulator.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

"Checked wiring behind dash, reseated all terminals on back of cluster and made sure everything on the circuit board were making good contact, put it together and still the surging continues."

Water from interior condensation & leaks wreaks havoc with the ammeter terminals, so I'd suggest taking a second look there.
Did you take the two wires (with ring terminals) off the back of the ammeter? The corrosion would be inside those connections. Clean the ring terminals, the studs and the contact areas for all that stuff. Look at the wire going in to each crimp on the two ring terminals to see if it looks burnt or green with corrosion. If you have enough slack, you can cut off the old ring terminals and install new ones on clean wire.

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"Louise", a 1976 Dart Custom project, (now sadly reverted to being just an "organ donor" to our other project Darts.)

Thanks for the responses! Ill have to tear into it again this weekend. I've been driving it all week it seems to be behaving still no amperage fluctuations.

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65 Valiant 4 door 3 on the tree 225 /6

65 Valiant 2 door Auto 225 /6

Spent another day off on this car. Tore the wiring "out" and checked over everything again. Fixed a few other things while I was in there too. Took the cap off the VR, found a burnt wire going to one of the terminals on the electromagnet. This might have been me in my testing that fried the connection. Anyway, re-wound the terminals with a new bit of wire and soldered it in place. Now I'm back to the heavy amperage surges again. This is the second VR I have gotten from the local napa. Could the surging still be a VR issue? I have this baby wired to ignition toggles, amperage still fluctuates from dead center on gauge to pegged full with the accessory circuit completely off and battery fully charged and in good health. It doesn't seem that the voltage is getting too high, but I also only ran it for about 10 minutes so far. Need to run to the gas station now.

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65 Valiant 4 door 3 on the tree 225 /6

65 Valiant 2 door Auto 225 /6