charging system trouble

-

dirt wagon

Active Member
Joined
Dec 7, 2012
Messages
37
Reaction score
4
Location
new orleans
On my 64 dart wagon with a small block and m/p electronic ignition, Im getting 15 1/2 volts at the battery. Over 16 volts when the lights are on. The battery leaks a little water around the top if I run the car for a while (20 minutes). The leaking was much worse before I installed a new voltage regulator. Still, im getting 15 1/2 volts at the battery when running. Is This too much?
The instructions for the electronic ignition says I should have no less than 12.5 volts at the ballast resistor. Im getting 12.3.
The alternator im using was given to me by a friend. It is a 2 terminal type.
All my wiring seems to be correct.
Any suggestions would be greatly appreciated. Thanks.
 
Under what conditions EXACTLY are you measuring this voltage at the ballast?

The possible causes are

Voltage drop in the ignition harness supplying the regulator

Voltage drop in the ground between regulator and battery NEG

Regulator out of tolerance

Bad battery

Do the following tests:

If your system passes the above quick checks, then it is likely something-------------


1....Could be a bad battery but not likely. "New" does NOT mean "good."

2.....Most likely it is VOLTAGE DROP in the ignition harness

3.....Also likely is poor grounding between regulator case and the battery

4.....In rare cases could be a bad regulator

TO CHECK voltage drop, do the following:

GROUND...........Run the engine at "fast idle," and make the following check first with all accessories off, then again with heavy loads, heater, lights, etc, turned on. Switch your meter to "low" DC volts. stab one probe into the top of the NEG battery post

Stab the remaining probe into the regulator mounting flange. You need to stab through any chrome, paint, or rust. What you are hoping for is a VERY low reading, the lower the better, and zero is perfect. More than .2V (two tenths of one volt) is too much and means you have a bad ground

VOLTAGE DROP. The regulator power source is also the voltage sensing terminal. This comes from the battery, through the bulkhead connector, ammeter, ignition switch, back out the bulkhead terminal through the harness, and to the VR. ANY voltage drop in this harness can cause OVER charging.

To check, Hook your meter to "switched ignition." This can be the 'high' side of the ballast resistor, or the blue field wire on the alternator. Turn the key to 'run' but with engine stopped. Again, with your meter on "low" DC volts, stab your remaining probe onto the POS battery post

As in the previous test, you are hoping for a low reading, the lower the better. More than .3V (three tenths of one volt) means you have a bad connection somewhere in that path.
 
Yes this is too much voltage at the battery ... the 'water' on the top of the battery is acid and is from the cells boiling with the overcharge. Don't keep driving it or running it for more than a few minutes 'til this is fixed! The battery could be damaged/ruined, and at worst, a few have been know to crack open if too hot, spilling acid everywhere.

It could be due to voltage drop as 67Dart273 is having you test. It could also be improper wiring to the alternator or a ground not being where it should. When you say the alternator is a '2 terminal', do you mean 1 big terminal (for the power output) plus 1 small terminal on the back (from the regulator, for the field), or do you mean 2 small terminal s on the back along with the 1 large power output terminal ?
 
The alternator has 1 large terminal and 1 small terminal. I havent had time to run the tests yet. Everything seems to be grounded well. And all wires are going to where they are supposed to. What do you mean by a ground not being where it should?
 
If it had 2 wires on the back (a 2 wire field) then if the control line for that type from the VR got grounded, the alternator would go to full tilt output. But you only have a 1 wire field connection so that is not it. Normal connections for your year car.

Is your voltage regulator a squarish looking thing with screw terminals, or a flat brick with a molded connector? Should be the former; just makin' sure no one snuck something else in there in the past.
 
Voltage regulator is rectangular in shape and has a screw connection for the field terminal and a slip on type connector for the other terminal. Spade connector i think they call it. The new one is the same type. I did the voltage drop test. I have 1.5 v at the ballast and/or field on the alt. I've been checking connections and even replacing wires 1 by 1. No change. I hooked up an alternator i had bought that is for a 71 fury and the voltage dropped to .09, i think. Didnt write it down. I dont know if this alternator is compatible with the system on the 64 dart. It looks a lot different. Could old wires and the resistance they might draw create such results? Theres not a lot of wiring between all these points. could it be the alternator? It was a guess that it was good when my friend gave it to me.
 
Voltage at the old style field is irrelevent.

You need to measure the voltage drop supplying the ignition voltage under the hood

The current path "in general" is

Battery........fuse link........through the bulkhead.........through the ammeter.......through the ignition switch......back out the bulkhead........to the underhood loads

Orginally these loads in that old car would have been the ballast resistor and the IGN terminal of your VR

Hook one terminal of your meter to the IGN terminal of the VR. Hook the other probe to battery POS. Set the meter to low DC volts, and turn the key to 'run' with engine off

If you measure more than .3V (three tenths of one volt) you have a problem in that path.

-------------------------------------------------------------

The second problem is VR grounding. Run these checks with engine warm, battery "normalized," and engine running "fast" to simulate low to medium cruise. Run this test first with all accessories off, and again with headlights, heater, etc turned on

Again with your meter on low DC volts, stab one probe into the NEG battery post. Stab the other probe into the metal mounting flange of the regulator. As before you hope to read a very low value, the less the better. Zero would be perfect. More than just .1--.2V or so means you have a grounding problem between the VR and the battery.

These two voltage drops, the drop in the ignition harness, and the drop in the ground, ADD to the VR voltage calibration. That is, if the VR is properly trying to regulate at about 14V, and if you have say, 1 V drop in the ignition harness, your charging voltage will be 15V.
 
One more thing. About the two field alternator. There is another terminal labeled field, that doesnt have any kind of connector on it. it would require a round 'eye' connector, that i hooked the field wire to, just trying things, and its grounded. In fact, I fried my new voltage regulator.
 
Thanks again for the info.It will be a couple days before I can get back to the car. Fuse link? You mean that smaller gauge wire thats hanging empty off the positive cable at the battery?
 
One more thing. About the two field alternator. There is another terminal labeled field, that doesnt have any kind of connector on it. it would require a round 'eye' connector, that i hooked the field wire to, just trying things, and its grounded. In fact, I fried my new voltage regulator.

We need to see a photo of what you are talking about. What you say SOUNDS like a "normal" pre 1970 alternator with one grounded brush and one field connector. The problem is, with "modern" rebuilts sometimes you don't get "what you think."

Your original should look 'sort of' like the one on the left. This is actually an oddball alternator. Your original would NOT normally have the hole at 3 o'clock with a brush missing. Yours would normally have an insulated field connector pictured at 12 o'clock, and the GROUNDED brush at 9 o'clock as shown

The EARLY seventies that use the later VR would look like the one at left, that is, "round back" but would have TWO insulated brush (field) connectors like the "squareback" on the right. The squareback came out around 73? or so and is a superior design. You can use the 70 and later, whether round or square, on your old VR, by grounding one of the two field connectors

 
Thanks again for the info.It will be a couple days before I can get back to the car. Fuse link? You mean that smaller gauge wire thats hanging empty off the positive cable at the battery?

The fuse link is in series. It is a fuse that feeds power from the battery, through the firewall, into the interior. I believe? that in your older car the "big red" and "big black" ammeter leads go through separate connectors, IE separate from the bulkhead connector.
 
-
Back
Top