Overcharging alternator and negative ammeter reading

[Dino]

In these situations a faulty alternator or voltage regulator is usually the cause but seeing as this is easily overlooked, make sure your fully charged battery measures around 12.6V between posts and make sure the battery terminal clamps are smothered in dielectric grease and tight.  Also check to see if the battery to engine, and the engine to frame ground straps are in good shape.   

[HANDM]

Yes it is a electronic voltage regulator
Single wire (green) at the alternator
Battery fully charged
All ground connections clean and tight

Checked blue wire (at regulator) key off- 12 volts
Grounded green wire, engine running with no increase in voltage output from alternator

[Pete in NH]

Okay,

I need to know exactly what type of electronic regulator it is. If it is the Chrysler electronic regulator it can not be used with a 69 single field wire alternator.

Again, I really need to know if the regulator is the flat rectangular Chrysler type with a 2 pin, triangle shaped connector on the front or some other type of electronic regulator. There are electronic type aftermarket regulars for 69's available and if that's what you are using I need to know that. That is why I asked for pictures.

If it is the Chrysler type regulator you need to change the alternator to a 1970 and up isolated field type. If you are using a true 1969 alternator you need a different regulator than the 1970 and up Chrysler electronic type.

[HANDM]

Okay,

I need to know exactly what type of electronic regulator it is. If it is the Chrysler electronic regulator it can not be used with a 69 single field wire alternator.

Again, I really need to know if the regulator is the flat rectangular Chrysler type with a 2 pin, triangle shaped connector on the front or some other type of electronic regulator. There are electronic type aftermarket regulars for 69's available and if that's what you are using I need to know that. That is why I asked for pictures.

If it is the Chrysler type regulator you need to change the alternator to a 1970 and up isolated field type. If you are using a true 1969 alternator you need a different regulator than the 1970 and up Chrysler electronic type.

Yes, I am using the electronic two pin triangle regulator bought at oreilly
I have a single green wire on the alternator so yes it is a 69 style alternator

Do I need to install a dual field alternator then? If so where do I run the new field wire to?
Thanks Pete!

[Pete in NH]

Yes, you need to install a newer isolated field alternator to work with that regulator. If you want to keep it looking somewhat like the original 69 alternator, get a 70 or 71 alternator. These were called "round back" alternators and will have two field wire connections.

One field connection will go to 12 volts. There is a blue wire that went to the ING. terminal of the original relay type regulator. This wire should now go to the blue wire on the electronic regulator connector and also continue on to one of the alternator field terminals. The other alternator field terminal should go to the green wire that connects to the green wire on the regulator connector.

You can also use a 1972 on up alternator. these are called "square Back" alternators. The back end looks different than the earlier alternators but, will fit and work fine. The square backs give you a little more output current and the diode assemblies are a little more rugged.

I would also get a new regulator as the old one may have been damaged by using it with the 69 alternator.

I think you should be all set and the long time problem should be solved. Good luck and let us know how it all worked out.

[HANDM]

Thanks Pete

I actually have a spare 72 alternator from a scrapped truck. I'll throw it in after work or this weekend and post back.
All the posts, all the replies and no one but you pointed out that it's the wrong alternator.......thanks again

[HANDM]

Installed the proper alternator and new regulator and it's now charging at 15.0... better than 18.0 but still seems a bit high?
It's an alternator out of a 72 Dodge truck with a 440 that checks out good at oreilly

[Pete in NH]

Hi,

While 15.0 volts may seem a tad high it may really be alright. Keep in mind that most every day voltmeters are at best +or- 2% accurate at best. that's + or- .3 volts so the actual voltage may be some where inside a .6 volt window. Many small meters are more like 3 to 5 % accurate. It's easy to get fooled by a digital meter that gives you an absolute number to forget that number has a calibration tolerance.

Also, these electronic regulators are supposed to be temperature compensated. When cold the voltage is up a bit. When the engine compartment and battery warm up the voltage goes down a bit. If you look in the factory service manual they give you a voltage range based on temperature. At -20F the range is 14.3 to 15.3 volts. 80F is 13.8 to14.4 volts, 140F 13.3 to 14.0 volts and above 140F less than 13.8 volts.

I think you system is working properly but if you still think it is too high you can swap regulators. I've not had good luck with after market regulators over the years and have stayed with Mopar regulators. The current part number is 4529794.

[Skull-1]

Make SURE the negative side cable has a damn good ground otherwise the alt. Thinks you always have a stone cold dead battery.

Can a battery disconnect switch on the negative post screw this up somehow?

Looks like I have a lot of work cut out for me on this thing....

I bet I have the wrong ALT / VR combo....

[Pete in NH]

It could, make sure everything is clean and tight. If you have one of those screw turn knob disconnect switches make sure its tight when the car is running. If the car cranks normally, it is likely okay.

[68charger440]

Just to give an update on the original problem here.  It is close to two months since I started this thread, and my electrical system still seems to be performing correctly.  After 40+ years of wrenching on these cars I will pass on one pearl of wisdom.  Electrical problems are much like cancer, They often spread from one area to another, and you may only be treating a symptom rather than the root cause.  You can make a change that masks the underlying problem for awhile, and then all of a sudden the little SOB rears its ugly head again.  Like with cancer survivors, the rule of thumb is that you don't declare that you are cured, you just count the years that you are cancer free.  After 5 years you can start to talk about being cured.  Sure there are simple electrical problems that are quick and easy fixes, but when you have a 45 year old electrical system with corrosion (cancer), cracked sheathing, and components overtaxed by loads that were beyond those originally spec,d causing intermittent disruptions in current flow, resistance, shorting etc. time is the real test of your repairs.  I have to laugh at those who read a short description of the problem and declare a sure solution.  Its better to point to the possible problems and solutions and let hard work, sound troubleshooting techniques and time prove you right.

[Pete in NH]

Absolutely right! One of the best tools in your tool box for keeping these cars working in the electrical department is a small inexpensive test meter and a plan for how to trouble shoot an electrical system. The meter doesn't have to be anything special a $10 to $20 Radio Shack special will do. Using what it can tell you sure beats guessing and replacing parts.

[68charger440]

Absolutely right! One of the best tools in your tool box for keeping these cars working in the electrical department is a small inexpensive test meter and a plan for how to trouble shoot an electrical system.

... and don't forget the best of all tools for most of us, that mushy mass between your ears!