1965 Dart Charging System Question

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Aaron65

Aaron65

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Hello everyone,

I've been fixing what isn't really broken today, and I have a few questions, just for the sake of my own education. I replaced a worn ignition switch, and I took a few voltage readings at various places. Here is what I found:

Key on, engine off:
Battery: 11.8V (this ranged up to 12.2 after I let the car run awhile)
VR at Ign.: ~10.7V
Ballast Resistor: ~10.7V
Ign. Switch Hot: 11.8V
Ign. 1 at the switch: 11.8V
Bulkhead connector inside the car: 10.7V

Key on, engine running for 20 minutes:
Battery: 14.3-4V
VR at Ign.: 14.0V
Ballast Resistor: 14.0V

I didn't check the rest with the engine running, but I think it's clear that I must have a corroded wire or something between IGN1 and the firewall. What I don't get is why the voltage drop is so much lower with the engine running. Can anyone shed some light on that?

Is there anything else between the ignition switch and the firewall? I actually changed out the connectors and a length of wire that seemed a little brittle at the switch, but that didn't change anything. It's obviously not something to lose sleep about; I've been driving it this way for years. I'm just curious at this point; it never hurts to learn something new. Thanks!

Aaron
 
Aaron65 said:
I didn't check the rest with the engine running, but I think it's clear that I must have a corroded wire or something between IGN1 and the firewall. What I don't get is why the voltage drop is so much lower with the engine running. Can anyone shed some light on that?
Click to expand...
Two reasons.
a. Voltage drops with increasing current through a resistance.
b. When the engine is running, power is coming from a different source - the alternator. Therefore current flows through different path for some of the journey.

There is another difference related to both of the above. Most devices draw more current when given power at a higher voltage. The battery only had enough charge to provide power at 11.8 Volts. In your running test, the alternator was providing power around 14.4 Volts.

However in your case, the voltage drop is greatest when powering from the battery.
That would suggest only b - the route is the cause.
To really know if the drop larger or smaller, measure the voltage at the alternator vs. voltage at the ignition wire.
 
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Alternator vs. Battery
This is the trick to understanding the main circuit.
The car has two power sources. Current flows from whichever one has the highest voltage. (unless there is really high resistance in a ground or route)

The battery and alternator feeds join with the wires to the various circuits at a welded splice.
We can think of this junction as the primary power distribution point.
From this distribution point, power can go to the headlight switch, the fuse box, and the key switch.
upload_2019-11-29_17-13-51.png
 
Aaron65 said:
Is there anything else between the ignition switch and the firewall? I actually changed out the connectors and a length of wire that seemed a little brittle at the switch, but that didn't change anything. It's obviously not something to lose sleep about; I've been driving it this way for years.
Click to expand...
If the insulation is brittle then likely at some point it got hot - too hot. I say likely - there may be other environmental causes - you know the car and its history and I don't.

As far as I know, the ignition wires all go direct to the firewall connection. But I haven't looked at a 65 or a 65 diagram to say absolute.
The alternator and battery feeds first go to the main splice as shown in the previpous post.

I forgot to mention that when checking the voltage drops from either the battery or the alternator, check the ammeter.
When using battery power, the ammeter will show how much flow is going out.
When running on the alternatior, the ammeter will show how much current the battery is using to recharge. A low battery seeing 14.3 Volts might be draw 30 amps, but one that is fully charged will draw zero. That's a big differenece when considering voltage drop. In the first case the alternator is providing current to ignition and maxing the rotor plus 30 amps to the battery. In the second case its providing power to the ignition and minimal to the rotor for a total of 2 to 4 amps.

upload_2019-11-29_17-39-9.png


Above scenario we can be confident that the voltage at the battery is the same as voltage at the main splice.
However we don't know what the alternator's output voltage is.

In the scenario below, voltage at the battery will be less than at the main splice. Because current is flowing through that wire, some resistance must be expected the wire and at each junction.
upload_2019-11-29_17-53-15.png
 
Thanks for the detailed replies, Mattax. I bought the car from Wildcat Auto Wrecking, so anything in its history is possible! Some wiring looks like it might have gotten hot in the past. I checked the alternator stud with the engine running, and it held at about 0.2V above the battery. The ammeter reads just to the right of center when the engine is running; it stabilizes within a few seconds usually.

Rather than undoing the whole wiring harness under the dash, I'm thinking about just running a new wire between the ignition switch and the bulkhead connector. I think you're right in saying that there is nothing else between the two, at least if I'm reading my electrical schematic correctly. Am I right in thinking that the ignition wire between the ignition switch and the bulkhead connector is 16 gauge?
 
Aaron65 said:
Am I right in thinking that the ignition wire between the ignition switch and the bulkhead connector is 16 gauge?
Click to expand...
Probably. Certainly not smaller. 14 ga would be OK too.
I made that circuit diagram based on the '67 Barracuda and Valiant wiring diagrams.
1965 has some differences at the bulkhead connector and there are probably other differences as well, but probably not the ignition feed.

There's a scanned '65 Plymouth service manual here.
MyMopar - Mopar Forums & Information - Service Manuals
If you have bandwidth, download that and check the Valiant diagram in the back of the electrical section.

Both ends of that wire are probably Chrysler or Packard 58 type female terminals.
It's not too difficult. Make it up on the bench and then install it.
Unwrapping the harness tape may not be any fun. I've cheated a few times by leaving the orignal wires in the harness and runing the new wire next to it. Tape or gently zip tie to keep it neat.

You'll have to remove the bulkhead connector on the engine side.
Then with a hair pin or release tool, depress the retaining tab on the terminal. Give it a little push and then go under the dash and it should be free.
 
Here's some tips on removal. I think the two multi-connectors on your '65 are similar to the these
question on the main harness plug on firewall
'65 has a seperate terminals outside of the multi-connectors for the alternator and battery feeds. Most of us think that's actually a better design.
edit: Just looked at a photo I took yesterday of '65 Satelite.
Connectors are a little different. Terminals will remove the same way though.
upload_2019-11-29_21-47-6.png


For new 16 or 14 gage terminals, this may help
Sources for Chrysler type wire terminals
 
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Aaron65 said:
I checked the alternator stud with the engine running, and it held at about 0.2V above the battery.
Click to expand...
So if the Alternator is running at 14.5 and the ignition feed at the ballast resistor is 14.0, that would be a 0.5 Volt drop.
And if the battery is 14.3 V at the same time, then .2 V is lost on the way to the main splice and .3 volts are lost on the way to the ballast resistor.
That's not bad. Some of that could be lost in the ground connections too. If you're curious about the drop in specific section of wire, place the voltmeter's positive lead on the output stud and the negative lead on whatever point you want to measure drop.

Aaron65 said:
The ammeter reads just to the right of center when the engine is running; it stabilizes within a few seconds usually.
Click to expand...
The ammeters are 40 amps to 40 amps, center zero. In other words, if the needle half way to the left side, 20 amps is going out. If its a quarter way to the right, then the battery is using 10 amps to charge.
 
I've done some more playing around. I ran a new section of 14 gauge wire from the ignition switch to the bulkhead connector, and I ran new wiring from the bulkhead connector to the ballast resistor and the voltage regulator. Here are my new numbers:

Key on, engine off:
Battery: 12.2V
VR: 11.6V
Ballast resistor: 11.6V

Key on, engine running:
Battery: 14.0-1V
Alternator: 14.3V
VR: 14.0V
Ballast resistor: 14.0V

It looks like I might have some voltage drop somewhere in the battery circuit under the dash. The ammeter connections are good, but any of that wiring, including the welded splice, could be a little worse than average. I think I'm going to leave it alone for now; it seems to be functioning pretty well.

The best thing is that it's idling a lot better now (which could have also been a high resistance ballast that was on it). I'm running an aftermarket orange box on it right now, but it's always had a light idle miss since I've been driving it, even with points and several carburetors. I think I might have just had a lot of resistance in the primary ignition circuit. Thanks for the help, Mattax.
 
I never can remember...........does your car run the ammeter through the separate very large posts through the bulkhead? some early A's did this. if not..........

Generally the voltage drop path for Mopars is this:

Battery...........starter relay big stud..........through fuse link..........through bulkhead on RED ammeter wire..........through ammeter......out the BLACK ammeter wire..........to the under dash WELDED SPLICE..........branch off that to the ignition switch connector............through the switch........back out the connector on (usually) DARK BLUE "ignition run"...........back out the bulkhead connector into the engine bay.

EACH POINT above that is a connection is suspect and there might be more than one. For example, drop might be right IN the igntion switch itself, and or in each of the connector terminals.

I've posted this before..........one way "around" this is to electrically cut the dark blue "ignition run" coming out into the engine bay.

Use the end coming out of the bulkhead to fire a relay.

Connect the engine bay end of that wire to the load contacts

Connect the feed contacts to a fuse/ breaker coming off the starter relay 'big stud.'

There are only so many causes of over charging

1....Voltage drop in the "hot" side harness, causing the VR to get low voltage
2.....Voltage drop in the ground side, the VR MUST see a good ground back to the battery
3....In rare cases, battery problems
4....A VR that is out of calibration, especially if the old mechanical type. Most new replacement ones are solid state, and most either work or not, but there can be exceptions.
 
There are two separate connectors through the bulkhead on mine. I'm pretty happy with 14V at the battery with the engine running, so I'll probably let it ride for now. Maybe I'm used to GMs and Fords, but I think that's within specification.
 
edited!
While running, just 0 .2 Volts between the alternator out and the main splice.
This looks good.
Some resistance in the feed, but not a lot.
upload_2019-12-7_19-16-7.png

Was the ammeter at zero during these measurements?
The battery seems low (12.2 V with key in run, engine off) so it might be taking a small charge ??
upload_2019-12-7_19-11-21.png
 
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0.6 V Does seem to be a somewhat big drop between the battery and the ignition with nothing else on. Could be battery feed or ground.

If you want to narrow it down..
With key in run, measuring at the alternator output will show the voltage at the welded splice (since there's no current in that leg)
upload_2019-12-7_19-33-0.png

If there is drop then measure between the battery positive and each of the next junctions.
Also check battery negative post to engine and body (grounds).
 
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Aaron65 said:
There are two separate connectors through the bulkhead on mine. I'm pretty happy with 14V at the battery with the engine running, so I'll probably let it ride for now. Maybe I'm used to GMs and Fords, but I think that's within specification.
Click to expand...
LOL Well batteries are batteries, at least the lead acid ones
 
Mattax said:
0.6 V Does seem to be a somewhat big drop between the battery and the ignition with nothing else on. Could be battery feed or ground.

If you want to narrow it down..
With key in run, measuring at the alternator output will show the voltage at the welded splice (since there's no current in that leg)
View attachment 1715434616
If there is drop then measure between the battery positive and each of the next junctions.
Also check battery negative post to engine and body (grounds).
Click to expand...

The ammeter always reads in the middle (just a touch to the right of center, actually) after a few seconds of startup. I'm sure I've checked the grounds, but I'll check them again next time I'm out there messing with it. I believe today that I checked the battery voltage going into the bulkhead connector and it was the same as battery voltage, which would seem to mean that my trouble is under the dash. I couldn't get my Power Probe all the way up to the ammeter today, and that's where I decided to quit. I'll try again with the multimeter next time.

I'll also check out the alternator output with the engine off and see what that says.
 
OK, I made a few more checks this morning. First, the battery is at least 6 years old, and I think it might be starting to get weak, although I haven't been driving the car a lot over the last week. Second, I'm not getting any significant voltage difference between the battery negative and ground, at least on firewall screws for the VR and starter relay (and block).

With the key on, engine off this morning, these were my readings:
Batt: 11.8V
Alt.: 11.4V
Upper Bulkhead (from splice): 11.4V
Lower Bulkhead (from starter relay): 11.6V
Starter Relay: 11.6V
VR Ign.: 11.1V

So I think the cable running to the starter relay could be changed, and there's definitely something under the dash going on. It's only losing .2V between the bulkhead connectors, but there's obviously something eating voltage before it gets to the VR, which is strange, because I changed that wiring yesterday (and it's better than it was). It looks like it might be the wire from the splice to the ignition switch itself.

I think I'm looking at an old car with old wiring here, and a bunch of small flaws are adding up. The probably answer is that I need to do some rewiring under the dash, so I'll put that on the eventual project list.
 
Aaron65 said:
which would seem to mean that my trouble is under the dash
Click to expand...
Yes, exactly. There are three terminal connections before the main splice and it is possible for the ammeter's studs to get loose. They are pressed into a metal plate so its pretty unusual. I don't know how hard it is to access on your car, but I'd do it this way. IF the voltage drops confirm its behind the dash, check at the inside of the bulkhead first. If that's OK, then disconnect the battery and check that the nuts holding the ring terminals to the ammeter aren't loose, and the studs arne't loose. If possible do a visual inspection of those terminals.

Without the engine running the wire from the alternator output to the main splice acts just like an extension of the voltmeter's lead.
I've not used the Power probe. I don't know how it works so hesitate to say this is true when using it.

When we measure voltage as we've been doing, we've been assuming no resistance in the ground paths.
The current returns from the rotor through the block, as does the ignition.
upload_2019-12-8_9-14-55.png


A way to isolate the drop is to directly measure voltage differences in the line where current is flowing.

Here's an illustrative example.
upload_2019-12-8_9-26-51.png


In this example, there is little drop in the first section of the battery circuit. However there is a big difference in the return from the alternator case to the battery's negative post. So in this example, most of the resistance is in the return path. Next steps would be to check the alternator to block and block to battery.
 
Updated with this mornings info.
upload_2019-12-8_9-37-46.png


Differences
0.2 V Battery positive to relay
0.0 V Relay to firewall
0.2 V Firewall to main splice
0.3 V Main splice to Regulator

Would like to see zero between battery and the relay since that's a bigger cable with ring or clamp type terminals. Otherwise typical. Lots of connections including the ignition switch between the main splice and the regulator. So some loss there is expected.

Yes. Get the battery charged on a charger and see if it will recover and/or get a new one.

My rules of thumb are:
Fully charged, good condition. 12.8 V with no load. 12.2 to 12.5 with small load. Above 10 V during start.

During and immediately after charging, a battery will develop a surface charge at a slighly higher voltage. So on a good battery, it might show 13.2 Volts immediately after shutting off the engine. That will disapate pretty quickly.
 
A Power Probe is pretty neat. I hook it straight to both battery terminals, and then the probe itself shows the voltage at any point it touches. I don't think it does ground differences, so I use my multimeter for that in the way that you explained. With the Power Probe, I can also power up devices using battery voltage directly. I figured out I had a bad horn relay in my Skylark that way.

I think I'll eventually replace the 10-gauge wire from the battery to the relay, since that's a pretty easy one. The battery is old, but the car sits for most of the summer, and it fires right up in the fall, so I'll probably leave it for now. With that being said, the next turn of the key could result in a click. :)

Thanks for your detailed diagrams. Between those and studying the FSM wiring diagrams, I've learned a lot about the Mopar electrical system.
 
Aaron65 said:
OK, I made a few more checks this morning. First, the battery is at least 6 years old, and I think it might be starting to get weak, although I haven't been driving the car a lot over the last week. Second, I'm not getting any significant voltage difference between the battery negative and ground, at least on firewall screws for the VR and starter relay (and block).

With the key on, engine off this morning, these were my readings:
Batt: 11.8V
Alt.: 11.4V
Upper Bulkhead (from splice): 11.4V
Lower Bulkhead (from starter relay): 11.6V
Starter Relay: 11.6V
VR Ign.: 11.1V

So I think the cable running to the starter relay could be changed, and there's definitely something under the dash going on. It's only losing .2V between the bulkhead connectors, but there's obviously something eating voltage before it gets to the VR, which is strange, because I changed that wiring yesterday (and it's better than it was). It looks like it might be the wire from the splice to the ignition switch itself.

I think I'm looking at an old car with old wiring here, and a bunch of small flaws are adding up. The probably answer is that I need to do some rewiring under the dash, so I'll put that on the eventual project list.
Click to expand...

Just follow the "road map." It might be right in the ignition switch contacts / ignition switch connector. Don't get distracted by such as the alternator unless there is some other problem. Concentrate on the two end "subjects" and what is in between..........that is, the battery, and the VR. Follow that specific path. Is it the blue "igntiion run" terminals in the bulkhead? Is it the igntiion switch connector? Is it the switch itself? You can access the switch, so you can check it fairly easily.
 
67Dart273 said:
Just follow the "road map." It might be right in the ignition switch contacts / ignition switch connector. Don't get distracted by such as the alternator unless there is some other problem. Concentrate on the two end "subjects" and what is in between..........that is, the battery, and the VR. Follow that specific path. Is it the blue "igntiion run" terminals in the bulkhead? Is it the igntiion switch connector? Is it the switch itself? You can access the switch, so you can check it fairly easily.
Click to expand...

I just replaced the switch and lock because the old one was loose, so we can rule that out (since the voltage drop got no worse and maybe a little better). I also rewired IGN. 1 from the switch out to the VR and ballast resistor. I really think the only thing left in that circuit can be the battery hot wire from the splice to the ignition switch. I think I checked that one yesterday (at the switch) and it was low, although I didn't make a note of it. That wire will be a bear to deal with in the car.
 
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Aaron65 said:
I really think the only thing left in that circuit can be the battery hot wire from the splice to the ignition switch.
Click to expand...
confused-gif.gif

Explain how you've concluded that.
Take your time. Walk through it. If you change your conclusion that's OK too.
 
When I was getting my fuel/temp gauges working, I was careful with the ammeter connections. They're tight and clean; I did that work less than a year ago, and I was able to look at them under the dash yesterday. They're good. I don't know if I mentioned that in my backlog of text so far.
 
I see. You're figuring "if I replaced or checked it, its good", so what didn't I replace.

I'm going by the voltage drop readings - and those don't agree with the conclusion that there is resistance in the "battery hot wire from the splice to the ignition switch"
 
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