My charging system is working ok ish but it seems to like charging at 14.5V to 15V most of the time and sometimes (usually at idle) it will surge back and forth from 13V to 16V.
I also read in another thread:
" the Electronic Voltage Regulator cannot have ANY circuit connected to it grounded " Could this have anything to do with it? my voltage regulator wire runs through a relay to the starter relay terminal on the firewall where all the other power stuff comes from. I have a ground wire going from the battery to the case of the voltage regulator as well to help with grounding everything. I just bought an optima battery and replaced my voltage regulator and the problem is less severe than it was but is still there. I can tell you the basic wiring from a schematic standpoint is all correct but is there some details I am missing?
Thank You,
Jerame

With the output surges, the voltage reference that the it uses to tell that it is putting out the right charge is dropping in level; perhaps the relay load or contacts are erratic. Or the main ground from the battery to chassis/block is erratic, and when it acts up, all the ground current in and out of the battery flows through that smaller wire, and that also will effect the reference.

Another possibility is an erratic short in the brush holder or on a wire to the alternator field if this is a later 2 wire field alternator.

Is this a standard Chrysler VR and alternator? And what year, model of car?

Is the relay the sends power to the VR powered by the igntion switch? And what other circuits and loads feed off of that relay?

BTW, putting in the new battery is probably making things behave better; it likely have better capacity to absorb the alternator surges.

Often most charging problems are caused by voltage drop in those related circuits on the ground side. Clean both battery cable connections, and negative connections to block, head to fire wall, and check with VOM for drop between battery negative post and chasses' of electronic spark control (orange box) voltage regulator, and alternator. One fix would be to extend your ground loop to pick up ESC, and alternator if needed.

All ground side connections should be voltage drop free to negative battery terminal. Voltage drop in plus side of these circuits is will be found in the bulkhead connector as charge electron flow goes from alternator through bulkhead connector, amp gage, and back out bulkhead connector to battery. Clean bulkhead connector brass, or if needed replace then with new.

Once you achieve voltage drop free connections, that leaves internal alternator, and or voltage regulator problems.

_________________
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

it is a stock charging system for a 73 duster. I have bypassed the amp meter (it went bad) but I will look for other voltage drops in the system.
The relay is powered by key on but its output is only the field wire. I do have the field wire running to the starter relay on the fender not the battery (along with a lot of other wires). I think I will try moving it directly to battery+. The ground side should be good as I added an 8 gauge ground from the battery - directly to one of the bolts on the VR case.
If I have something odd going on in the windings of the alternator should that be detectable on one of those parts store testers?

The Piper Cherokee airplane used a Mopar setup for charging. Airplane regulations demand a detailed knowledge of the parts and functions in a plane. If you really want to know your charging system in detail, you should download and read this commented overview, it's the best I've seen. Next time, you're the guru!

Piper-Charging-System.pdf

Olaf

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Aspenized

Just getting back to this.....OK, I think I understand the relay powering the field. Sounds like it duplicates the ignition switch's ON position and you should have 12V to one of the 2 field connections on the alternator; correct me if I am wrong.

The way in which this '73 system works is that +12v goes to one field terminal and the regulator pulls a varying amount of current from the 2nd field connection to regulate the alternator output. Output surges are caused by either:
1) the wire from the VR to the 2nd field terminal getting grounded and pulling too much current through the field; this can be caused by
- a short in the wire from the VR to the 2nd field terminal
- an internal short in the field winding; this can be in the brush holder or in the field winding itself
- a short in the VR output to ground
2) The VR commands too much field current, caused by its reference voltage being too low, as discussed before. This could possibly be the ignition switch or the intervening wiring. I would put a voltmeter on the 12v to the VR and see if it is steady.

For wiring changes, I would connect the VR's I terminal to the relay 12v output in addition to the 12v going to the 1st field wire. In that way, both voltage sources to the field and regulator are identical, and there will be no chance of the 2 voltages changing relative to each other. This is the way the factory wired the car originally (and for good reason).

The relay is to duplicate the ignition switch on position. It eliminates any portion of the charging system current from going through the bulkhead connector. I like your idea of wiring the voltage regulator sense pin to the relay to eliminate drop coming through the shared wire. Any idea if I could wire this directly to the battery or would it cause a power drain with the key off and/or overheat my voltage regulator module?

Wiring the VR feed direct to the battery will not hurt it, but it will have power all the time and will being putitng current in the field to try to command the alternator to put out power even when the alternator is not turning: big power drain. So, yeah, not a good idea. Also, there was a recent thread on some forum of how this caused the alternator to be less stable. The OP in the thread ended up moving the VR power feed to the starter relay's big terminal and it stabilized the operation.

I played with my electrical system more and tried hooking my voltage sense wire to the main starter terminal. It eliminated the voltage fluctuations but made me charge at 15.5 volts consistently. Since it did have a dramatic effect I moved the sense wire to a place closer to the alternator. (a wiring block that most of the car runs off of) This eliminated both the voltage fluctuations and the overcharging. I did not end up needing to separate the sense wire from the field coil power wire but I think that would be the best way to do it. So if someone has symptoms like mine try moving the voltage sense wire to another location in the power circuit.

This over charge condition is a result of voltage drop either in plus side of circuit between alternator and battery, and or ground path of that circuit including any voltage differential between chasses of voltage regulator (its bracket screwed to fire wall) and negative battery terminal. You have a total of about a 1.2 volt drop somewhere, or several smaller drops through connections or conductors which add up to 1.2 v; find them, clean or replace them and charging rate will fall into normal range.

Also if you are running an electric choke and it is being supplied by any conductor in ignition circuit that may be you problem. A parallel path to ground will drop voltage levels in the circuit enough to cause an over charge of about one volt or more. To check if this is happening disconnect electric choke supply wire while taking charging circuit voltage readings. If voltage falls into normal range, make provisions to feed electric choke via a relay from battery, and triggered by ignition circuit. Relay requires very low current flow to activate it, and will not upset voltage level in ignition circuit enough to cause an over charge.

Happy hunting.

_________________
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