No charge at battery

[Tylan]

Alright, here we go again.

I've had this problem for a while, and it's really been messing with my head the whole time.
I asked about it in this other thread about a year ago now, where 67dart and Mattax tried their best to help, but unfortunately to no avail.

I recently got inspired to tackle this again, and went as far as just ripping out the interior wiring harness, which wasn't really too bad. By doing this I could get a better grasp and test the resistance of every single wire; which by the way, every wire in this harness seemed to be within reasonable ohm readings, under 1 ohm.

Then, since I had a better view of every wire in the harness, completed only the blue alternator field circuit (at least up to the alternator), shown by this diagram given by Mattax in the other thread: A1A-10R > 12-BK > Ignition switch > Blue run wire > J2 (only the blue wire connecting to the alternator)

This isolation test showed that this lone circuit is good, since it had the same voltage as the battery, albeit with a insignificant 0.05 volt drop. Adding in only the volt regulator (J2B) and ignition module (J2A) didn't cause any significant voltage drops when probing the same field wire from before. It was only until I reconnected the ignition coil did the voltage drop I know and hate occur.

So far, the situation has been whether or not the engine is running, if everything minus the radio, heat/ac control module and heater fan, as well as the wiper motor, is connected, the battery would show 12.3-12.4 volts, while running. And the blue alternator field wire would be getting closer to 11.8 volts. I could be wrong, but I imagine the fact that the alternator field getting less voltage than the battery itself holds is the reason why the alternator is not charging the system.

When doing my recent test, today in fact - and remember, it is just the ignition coil and blue field circuit containing power for this particular test, with the engine off - I get the same readings: 11.8-11.9 volts at alt. field, 12.3-12.4 volts at battery. I also probed the positive post of the ignition coil - not sure why I didn't do this before - and it read closer to 6 volts (which is normal I believe, and not of concern of mine unless that is, in fact, off).

So, my dilemma is: field wire not getting full battery power with ignition parts plugged in, which I know now, rather than being clouded with so many possibilities, because this time I've narrowed down the problem area. Is there an issue with my ignition module? voltage regulator? ignition coil? The ignition module and voltage regulator are pretty damn new, so I wouldn't immediately point them out as the problem, but still not eliminating them as possibilities.

But here's an important question: do I even have a problem at all, or am I chasing a phantom issue, making an issue where there is none? I was certain, no matter the year, a 12v system using a 12v battery should always charge the battery to around 13 to 14 volts if functioning properly, but I suppose I could be wrong.

 

[Oldmanmopar]

Pull the Pos. battery cable off while running and see if it shuts off. If it stays running start turning things on one at a time until it shuts off. You found the draw.

 

[67Dart273]

Pull the Pos. battery cable off while running and see if it shuts off. If it stays running start turning things on one at a time until it shuts off. You found the draw.

Steve I'm surprised at you. This is a fake "test" and can cause damage to modern electronics.

It also is not really testing anything, because, if the engine happens to be running slowly enough that the "good" charging system is not putting out much, the engine may die and lead you to falsely believe that it is not charging
If the alternator is merely "down" from full output, like, maybe, 2 or 3 or 4 open diodes, the engine may keep running and lead you to the false conclusion that the charging system is OK

 

[67Dart273]

A short review:

Wiring harness have voltage drop I don't care how good condition they are, unless you have taken steps to vastly over-design them. That is, the field wire, supplied by the ignition switch, WILL have "some" drop even if only a few hundredths of a volt. Bigger wire, better connections, relays will change this, sometimes a tremendous amount.

The charge path, AKA the path from the alternator output, through the bulkhead, the ammeter, back out the bullkhead, and all the terminals in between will have some drop. This is (mostly) not that serious, because the regulator will ramp up the voltage until the sensing/ ignition terminal is "satisfied" at the VR setpoint. That is nominally 14V

I wish I could be "there" for some of you, because teaching "voltage drop" is not that difficult, but it is a lot easier if two guys can "see" eye to eye.

This, still, gets back to "the path." The circuit path of the field wiring to the VR from the battery, the grounding of the VR to the battery, and whether or not the alternator is actually performing. That is, "maybe" it has a partially shorted rotor, and even though the VR is trying to send the rotor full current, the damn thing is just simply not putting out. This can usually be determined by following the manual, full output tests Bypass the VR and determine if the alternator is "able."

Bad diodes can limit output, but these also almost always cause ripple, which is easily found by monitoring with a voltmeter on AC range, or noise in the radio if equipped.

Many guys who know me know that I dislike "throwing parts" but sometimes it will fix things in desperation, and sometimes it will at least tell you that you are on the wrong track!!!

 

[Dana67Dart]

All of this has to be done with the engine running all OEM wires hooked up, VR. Grounded etc.

My 67 single field wire round back alternator gets 5 to 6 bolts from the regulator when the load on the alternator is low. When the load is higher the voltage goes up. Measuring the voltage from ground to the field will get you this value.

The same would hold true for the later v shaped VR. BUT... .the input to the alternator field is battery voltage and the ground is varied by the VR. checking the voltage between the two field wires will show the votage the field is getting.

 

[Oldmanmopar]

Steve I'm surprised at you. This is a fake "test" and can cause damage to modern electronics.

It also is not really testing anything, because, if the engine happens to be running slowly enough that the "good" charging system is not putting out much, the engine may die and lead you to falsely believe that it is not charging
If the alternator is merely "down" from full output, like, maybe, 2 or 3 or 4 open diodes, the engine may keep running and lead you to the false conclusion that the charging system is OK

Never said I was an electrician. LOL. Always worked for me. I drove cars to the trailer without a battery. Jumped them with the yard truck and drove them .
When the battery is dead in my trailer I would take the battery out of the truck. Use it to winch the car on while the truck is running then put the battery back in the truck. I never had a problem. Maybe I just got lucky for 50 years. Many times I would test to see if it is charging by removing the Pos. cable. If it shuts off its not charging.

Just did it with my Daughters Mini Cooper S. She left her lights on and the cables wouldn't reach to her trunk how she was backed in on a hill. Started her car with my battery and put the cables back on hers while running.

 

[Tylan]

This, still, gets back to "the path." The circuit path of the field wiring to the VR from the battery, the grounding of the VR to the battery, and whether or not the alternator is actually performing. That is, "maybe" it has a partially shorted rotor, and even though the VR is trying to send the rotor full current, the damn thing is just simply not putting out. This can usually be determined by following the manual, full output tests Bypass the VR and determine if the alternator is "able."

Many guys who know me know that I dislike "throwing parts" but sometimes it will fix things in desperation, and sometimes it will at least tell you that you are on the wrong track!!!

While I can't say for certain, I am confident the alternator itself isn't the problem. This being my third alternator during this whole debacle, I don't have too much reason to think the alternator itself is acting up, especially considering that I had the thing tested last year and it was given the OK. As I said before, the VR and ignition module are fairly recent parts, the VR being replaced around the same time as the alternator. The ignition module I can't say, it was replaced by the previous owner, but it still has the same shiny glossy finish the VR has, so I have to assume it's a newer replacement as well. Now again, I will acknowledge that I cannot guarantee the condition or state of these parts, this is my first classic mopar after all, and I'm learning as I go along. I had wire-brushed the mating surface of the VR to the firewall, presumably assuring a good ground, but perhaps I need to check it again.

The same would hold true for the later v shaped VR. BUT... .the input to the alternator field is battery voltage and the ground is varied by the VR. checking the voltage between the two field wires will show the votage the field is getting.

That's the thing, I know the field CAN get full voltage, but it doesn't with the ignition in. The reason my thoughts point towards something in the ignition circuit is because the test results I got from isolating the field circuit and later connecting the ignition, are the same exact results I got from having everything else plugged in. Which tells me the issue lies somewhere within the field or ignition circuit. I am aware the ignition system is supposed to draw some power when the key is turned to run, which is why the battery goes from 12.6 (12.8 in my case, after having it on a charger) down to 12.3-12.4 volts. What I don't understand is why the field circuit goes from full 12.6 volts when it's isolated, down to 11.8-11.9 volts when I simply provide the ignition coil power. About 2 tenths V is drawed by the ignition, but where the hell does the extra 3-4 tenths V go that previously powered the field???

 

[Mattax]

When doing my recent test, today in fact - and remember, it is just the ignition coil and blue field circuit containing power for this particular test, with the engine off - I get the same readings: 11.8-11.9 volts at alt. field, 12.3-12.4 volts at battery. I also probed the positive post of the ignition coil - not sure why I didn't do this before - and it read closer to 6 volts (which is normal I believe, and not of concern of mine unless that is, in fact, off).

This all seems about right.

What I don't understand is why the field circuit goes from full 12.6 volts when it's isolated, down to 11.8-11.9 volts when I simply provide the ignition coil power. About 2 tenths V is drawed by the ignition, but where the hell does the extra 3-4 tenths V go that previously powered the field???

part A
Voltage drop increases with more current.
The both the ignition box and the coil draws current when the key is in run.

The electrons move only when the circuit is completed.
When there is no movement there is no resistance.
When the electrons move, that's current.
Resistance to movement reduces the energy level.

Take a 1/2 ohm ballast resistor.
With the points open, electrons aren't moving. Voltage on the battery side, engine off/key on, is 12.5 V.

Close the points and current flows through the circuit.
The number of electrons moving is the same, but the energy level drops.
Change in Voltage = Resistance x Current

part B
The battery's voltage gets pulled down when its under load.
Battery potitive to nevagive post will be 12.6 Volts with nothing pulling on it, but turn on the dome light it will drop a little.
Turn on the ignition and field, step on the brake, and it will drop more.

Here's what the battery voltage looks like when the key is turned to start

Battery energy level drops from 12.8 Volts to 10.1 Volts and stays down there when the key is in start.

 

[Mattax]

And the blue alternator field wire would be getting closer to 11.8 volts. I could be wrong, but I imagine the fact that the alternator field getting less voltage than the battery itself holds is the reason why the alternator is not charging the system.

The regulator should be full fielding (allowing current through the rotor full time) with such low voltage.

Lets start from the beginning. What was the problem you are observing.
Was it that the ammeter shows discharge when the car is running?

 

[Tylan]

Lets start from the beginning. What was the problem you are observing.
Was it that the ammeter shows discharge when the car is running?

Unfortunately, as I said once before, the ammeter is corroded to pieces, needle is not going to stay in place. The two wires that connected to the ammeter are currently spliced together, and have been since I had my hands on the Duster.
The reason I believe there to be an issue is because I just happened to check the battery voltage while running and noticed it was lower than the expected 13-14 V range, 12.4 volts. I know that at some point the battery had been getting charge before.
But, perhaps I am looking to far into this, just giving myself trouble. I am just the kind of guy that wants things working, rather than having to put the battery on a charger after every time I run it.

 

[67Dart273]

Somebody mentioned "start over" I think. "Back to basics"

Is this a grounded field with the older 69/ earlier VR or the newer isolated field (two field wires) with the newer "flat" electronic VR?

First make sure SURE that the VR is grounded, and that the ignition terminal is getting full battery voltage

if so "full field" the alternator and see what happens. If grounded field, remove the field wire and jumper 12V battery to the field wire, slowly bring up RPM while watching a volt meter. If battery is low it might run a bit lower, but it should bring up at least 15V

If not change meter probe to alternator output stud and see what that voltage does. If it stays "at battery" it's not charging. If ti goes "way high" and the battery V did not follow, there is a break in the charge wire path.

Look in the manual for destructions on checking field current.

 

[Mattax]

Unfortunately, as I said once before, the ammeter is corroded to pieces, needle is not going to stay in place. The two wires that connected to the ammeter are currently spliced together, and have been since I had my hands on the Duster.

Sorry I didn't remember. Can't remember my own stuff half the time never mind other peoples.

The reason I believe there to be an issue is because I just happened to check the battery voltage while running and noticed it was lower than the expected 13-14 V range, 12.4 volts. I know that at some point the battery had been getting charge before.

You are correct, system voltage should be the same everywhere, and only drop in places where current has gone through resistance.

Measure the voltage at the alternator output, and then at the regulator input - or with a '73 as close as you can get. That will probably be the ignition junction on the ballast resistor or the field connection with the blue wire.

Field current test is worth doing. With a isolated field alt, one brush is grounded and the other connected to power. The meter must be set to handle at least 10 amps, and then connected in line with the probes in correct jack on the meter.

 

[Tylan]

After some fiddling, the battery charges now. Directly ran some wires from the field terminals to the battery, proved the alternator is ok, had an output of 16 volts. In the end, deciding to replace the VR seemed to fix it right up . My stubborn mentality refused to believe the thing could fail so quickly I suppose, but I've heard from a few other old chrysler drivers that the VR is a very common fail area, which influenced me enough to attempt to claim the warranty on the "old" VR I got about a year ago (Didn't work, 8 days too late, darn), and replace it.
So the lesson here: kiss principle. Don't let yourself eat up hours upon hours of fiddling around when the issue could lie right under your nose.
Now to sort out the brand new no-running deal.... wish me luck.

 

[Ironracer]

Right on! These Ol Boys here Are Sharp! That said, I've been Through MANY VRs, from the local chain store. All Chinese. Summit has the MP, USA made ones for a Lil more. Solved my issues... well, at least that one! Lol

 

[Dana67Dart]

Glad your problem is solved ( for now)


FYI...
My VR is electronic but of the 1 field wire variety.

With the engine turned off but the key in the run position I got 9.5v out of the VR to the field wire to the alternator.

With the engine running at idle it was in the 5 to 7v range and when running off idel 1500 to 2000 rpm it was about 2 to 5v

Engine had just been started but ideled for about 3 minutes before I took the measurements.

 

[67Dart273]

Glad you have it working, but some comments

There ARE things that take out a VR. Shorts in the harness, or shorts at the brush assemblies in the alternator. If you read the book, there is a procedure to check field amperage draw. Fields can get intermittent/ random burned or bare windings and cause partial shorts, causing them to draw more than proper current. This can burn up regulators