'71 Duster 340 Battery getting overcharged

[67Dart273]

at 2500-3000 rpm 14.5-15V...seemed to average around 14.7. Should I declare victory or is 14.7 too high? .

This is passable but you likely have voltage drop in the ignition harness. That is what the test was about "in part". You want the VR IGN terminal to be as "same as" the batter as you can get. Every single 1/10 'th of a volt drop in the ignition circuit ADDS that much to the charging voltage. That is, to say, if the regulator is "trying" for 14, and you have .7 v drop, that will give you the 14.7

That is not dangerously high, for now

 

[67Dart273]

The only thing I don't like is the voltmeter in the dash fluctuates rapidly intermittently at idle...is that normal? Seems to stay steady around 13.5-14 volts at high rpm..

It should not fluctuate. Does your meter at the battery show this? Might be a wiring problem under the dash.

 

[MrDuster]

I'm going to have to wait till my buddy can come over to answer that question. It's intermittent and we'd need a guy out at the battery when it fluctuates at the dash. I'm back on "family time" now about to play some checkers with my 4 yr old. I have to fix the melted plastic connector which takes power through the main harness plug on the firewall. When I look at that next week I'll look for signs of other wire issues. THANKS for the great advice and pictures, you were very helpful. I'll let you know what I find when I get back to it towards the end of next week. THANKS again.

 

[67Dart273]

You're welcome. Making progress....that's the main thing

 

[swinger1969]

Your voltage regulator is no longer in the circuit. Here's how the 70 and later systems work

Refer to the simplified diagram from MyMopar

The blue field wire comes direct from the switched 12V "ignition run" circuit. The 70/ later regulator GREEN wire controls sort of "the amount of ground" on the green wire.

YOU MUST HAVE an isolated field alternator (2 field terminals) in order to use the flat 70 and later regulator

You have three possibilities

1...Take a real good look at your alternator. Post a photo if you can. Some modern rebuilts are actually an isolated field unit that has one terminal grounded. In that case you can get different brushes and convert the unit, or maybe just some insulating washers and "unground" the brush

2...Replace the present alternator with a 72/ later (called a squareback, do not accept the older "roundback) and hook things up correctly

3...Keep the present alternator and buy a 69/ earlier replacement regulator

Below is a couple of different alternators. The one on the left is a special unit. This is an inferior old roundback, which originally came BOTH in 69/ earlier with grounded field, and 70 / later with isolated field. The one in this photo can be set up for EITHER and as shown has a grounded field

The right side photo is a "squareback" the better, newer design. All of these are "isolated field" (2 field terminals"

Below is a "rebuilder's hack." What this is, here, is an OEM 69/ earlier (grounded brush) with the grounded brush in place. The rebuilder has drilled an extra hole at 12 o' clock to insert an insulated brush and "convert" the unit to isolated field. These, for the most part, are a poor idea.

This is mind boggling! Turns out I have the square back alternator( see pic) on my 69 Dart 340 with one wire going to the term at the 12 position and one to the output terminal, and I have a VR that's a black box with a terminal ( IGN) on the bottome and a terminal ( field on the top and that's it. So what's wrong with this??? The guy I got the car from really mickey moused a lot of things so this doesn't surprise me!

 

[67Dart273]

Are you sayin it charges OK? Only one explanation if it does........the remaining brush holder has had the insulating washer removed and replaced with a metal washer

Remove the field wire and check for continuity from the field connection to ground. I bet it shows continuity.

If so, cut off that spade terminal so you don't accidently connect the field wire to the grounded one.

If it does NOT charge, ground that remaining field terminal

EDIT. Just saw your post in your other thread. That is troubling. 16V is too high as if the VR is not doing anything.

FIRST unhook the field wire and see if it stops charging. Check for continuity as I first said above.

Then see if the VR is mounted tight and grounded.

 

[67Dart273]

Now I'm baffled! I recently noticed that my headlights ( and maybe tail lights as well) pulse / flash on and off and can't figure out what to start checking! When I bought the car ( 69 Dart Swinger) it had this alternator in it, which looks like it's a 70, and charges high ( about 16 V) at higher RPM and goes down to about 14.5 at lower RPM. There are two "field" terminals on the back and the battery output, but wires only going to the output and the terminal at 12 o'clock. Is this wired wrong? What else should I be checking? The guy that I got the car from did a lot of pretty mickey mouse stuff so nothing surprises me!

Your original post. Let's stay in this thread for simplicity The way that is hooked up, it should not be charging AT ALL

 

[swinger1969]

Your original post. Let's stay in this thread for simplicity The way that is hooked up, it should not be charging AT ALL

Again, sorry bout that. So how should it be hooked up?....this is the way it's been since I got the car a couple of months ago and it's always showed it charging , but lately it's been showing 16 volts on the voltmeter. The regulator is the "little black box" kind with one terminal ( field) up top and one terminal ( IGN) on the bottom.

 

[67Dart273]

OK, pay attention, LOL

1....the way it's hooked up now it should NOT be charging at all, WHY? Because the field winding has no connection.

2....The fact that the system IS charging means that either that field terminal is actually grounded because someone removed the insulator, or else

3....There is actually something wrong with the field, meaning it's internally shorted to ground

4....The fact that it runs up to 16V means either the voltage regulator is not actually in the circuit, or that it's not grounded, or that it is malfunctioning.

==============================

5...How to fix? Start by reading my previous post:

Are you sayin it charges OK? Only one explanation if it does........the remaining brush holder has had the insulating washer removed and replaced with a metal washer

Remove the field wire and check for continuity from the field connection to ground. I bet it shows continuity.

If so, cut off that spade terminal so you don't accidently connect the field wire to the grounded one.

If it does NOT charge, ground that remaining field terminal

EDIT. Just saw your post in your other thread. That is troubling. 16V is too high as if the VR is not doing anything.

FIRST unhook the field wire and see if it stops charging. Check for continuity as I first said above.

Then see if the VR is mounted tight and grounded.

Once you have done the above, if it continues to run at too high voltage, check the power TO the VR. This is IMPORTANT. You must do this carefully and exactly

Hook one probe of your meter to the VR ignition terminal, or to the ignition power coming into the ignition ballast resistor. This is the power coming FROM the ignition switch.

Hook the remaining probe to the battery POSitive post. With key in "run" and engine stopped, post the reading. You are hoping for a very very low reading, the lower the better.

If this reading is .3V (3/10 of one volt) or less, replace the VR

 

[swinger1969]

OK, pay attention, LOL

1....the way it's hooked up now it should NOT be charging at all, WHY? Because the field winding has no connection.

2....The fact that the system IS charging means that either that field terminal is actually grounded because someone removed the insulator, or else

3....There is actually something wrong with the field, meaning it's internally shorted to ground

4....The fact that it runs up to 16V means either the voltage regulator is not actually in the circuit, or that it's not grounded, or that it is malfunctioning.

==============================

5...How to fix? Start by reading my previous post:




Once you have done the above, if it continues to run at too high voltage, check the power TO the VR. This is IMPORTANT. You must do this carefully and exactly

Hook one probe of your meter to the VR ignition terminal, or to the ignition power coming into the ignition ballast resistor. This is the power coming FROM the ignition switch.

Hook the remaining probe to the battery POSitive post. With key in "run" and engine stopped, post the reading. You are hoping for a very very low reading, the lower the better.

If this reading is .3V (3/10 of one volt) or less, replace the VR

Turns out that terminal that's not hooked up on the alternator is actually grounded. I dropped by a buddy's shop and he checked it out . The VR was one of the "non adjustable" digital ones and was faulty so we replaced it with an "adjustable" one and it seems to be fine, so far! Thanks a bunch for your help........and patience! :???:

 

[67Dart273]

Very good. I would cut that terminal off so you don't "make a mistake"