Can't get more than 12.5 volts thru charging system

-
Crusty Brian

Crusty Brian

Active Member
Joined
Jun 2, 2019
Messages
35
Reaction score
26
Location
Tacoma WA
I'm on my 4th voltage regulator, this last one was one of the upgraded solid state guts ones (it came from a dude in Texas but has made in China stamped on it?) The gauge has never pegged out and this last one worked great for about 5 car rides! The gauge reads low and I'm getting @ 12.5 when checking at the battery(including having the lights, heater and wipers going). The alternator (single wire) tested good. For a minute if you brought the RPMs up it would sit in the middle of the gauge like it should. 67 dart 273, 4 barrel (stock electrical, including factory radio) also my 66 Town & Country is doing the same thing
 
A lot of threads on the subject.
For the below tests, all accessories should be off.

What voltage is fully charged battery with key in off position?

What voltage with engine running.

Where does charge indicator sit key off.
Where does charge indicator sit with the engine off but key in run position

Where does charge indicator sit with engine running.
 
Wiring is to old! Look deeper and stop replacing. You need the Del + look!
 
1969383S said:
Wiring is to old! Look deeper and stop replacing. You need the Del + look!
Click to expand...
Another one that needs to tell the full story.
If its a 'one wire' then the regulator is internal....
 
12.5 is not really charging at all. Start by running engine on fast idle. Check power at IGN terminal of voltage regulator. That reading should be very close to same as battery. This is the "push on" terminal not the screw terminal. Next measure battery voltage, and then measure the output "big stud" of the alternator. If it is 'way high' much higher than battery, you have a break in the charge line/ ammeter/ bulkhead connector

If that stud is low, same as battery, it is not charging.

Next, jumper a wire from the alternator field terminal to the battery. This should cause full tilt charging. Raising RPM should cause the battery voltage to climb. Try to keep it under 16. If that does nothing, inspect the brushes, fix them, or replace the alternator
 
Dana67Dart said:
I assumed it meant round back 1 field wire vs. square back 2 field wire.
Click to expand...
Ok. Maybe.
Brian will have to tell. Also..
Crusty Brian said:
The gauge reads low
Click to expand...
What gage?

The gage labeled C-D sometimes also 'alternator' is an ammeter on the battery feed.
Charge and Discharge reference the battery, not the alternator (even though it may be labeled alternator).
During starting, the battery will show discharge.
After starting, if the alternator is working, the battery will recharge as needed.

Here's how Chrysler explained it in one of their 1960 Master Tech booklets.
upload_2020-4-26_20-34-45.png


Heck lets see if this animated illustration works. Just reload the page to get it to repeat.
Basic-Charge-Circuit-Charging-animated.gif
 
Last edited:
Oooooh anamation, your images are taking a huge step forward. I like it
 
That might be but it' d be helpful if we actually fixed the problem before going into the theory of a B-29 electrical system LOL
 
Crusty Brian said:
By one wire, I meant 1 field connection not two (later mopar alternators) it also has the battery stud, sorry
Click to expand...


Ok we are staring to get a little farther down the line.

When you reported 12.5 volts was the engine idleing or at say 2000 RPM.?
 
Yeah I said when you brought the RPMs up it sits where it should be (13.5ish) I'm suspecting bad ground at the firewall
 
Crusty Brian said:
By one wire, I meant 1 field connection not two (later mopar alternators) it also has the battery stud, sorry
Click to expand...
No problem. Thanks for clarifying. Yes single field wire.
Crusty Brian said:
Yeah I said when you brought the RPMs up it sits where it should be (13.5ish)
Click to expand...
Honestly, that's barely in the specified range, especially cold. The service test is generally with the engine held to 1250 rpm, it should be able to provide something like 25 amps with the voltage at 15 V. The exact number of amps varied with the alternator. But what your doing by turning on the lights and heater fan is an OK substitute. The only question, and its a BIG question, is how much current the battery is drawing.
If the battery is low, its going to be sucking a ton of power trying to recharge. Do the test with the lights and fan after the battery is fully recharged (ammeter showing zero).

Crusty Brian said:
I'm suspecting bad ground at the firewall
Click to expand...
Possible, but not likely.
The black wires shown in the diagram are all hot (positive) wires. Chrysler used black for the alternator output wires and other feeds.
The schematic does not show the ground wires.
To be complete, it should show the electric flow back to the alternator case (its ground) from the battery and the spark plugs..
upload_2020-4-27_9-52-59.png


So yes, if there are bad ground connections between the alternator and the block and the battery, this will throw off the voltage differences; but we don't see evidence to come to this conclusion from what you've posted so far.

1. See what the ammeter is indicating under each condition. (idle rpm with no equipment on, fast idle with no equipment, etc etc)
If the battery is charging, then let it fully charge. If it is charging heavily, put it on a charger. This is much much better using the car's system to bring up a drained battery.
2. Then measure voltage to ground at different locations under each condition. Battery positive , alternator output stud and ignition run connection to regulator.
3. If there are differences, then measure for voltage between ground locations and measure voltage differences along the current paths.

'67 Dart would have one ground cable from the battery to the block, and a smaller ground wire from the back of the block to the firewall near the blower motor.
 
67Dart273 said:
That might be but it' d be helpful if we actually fixed the problem before going into the theory of a B-29 electrical system LOL
Click to expand...
We are helping people understand the gages in a '67 Dart.
Chrysler figured drivers were smart enough to have instruments instead of idiot lights. They are more useful once you know what they show.
A lot of people don't know what the ammeter shows. The fact Chrysler often labeled it an alternator gage only adds to the confusion now.
 
Last edited:
Go back to the mechanical regulator and adjust it per the FSM, easy to do and with the cover off you can see what it is actually doing also.
 
I really don't think op has an issue.

12.5 v at idle with all accessories on, I say that is normal.

13.5 at RPM, battery is charging.
 
Yep, 13.5 to about 14.0 or a bit more with the car running & driving should do it.
 
Where did the OP say he was getting 13.5? I'm missing something.
 
67Dart273 said:
Where did the OP say he was getting 13.5? I'm missing something.
Click to expand...
Post #14.
Back at post #1, he wrote that bringing rpms up put the needle in the middle of the gage.
Soooo. Reading between the lines I'm assuming this gage is the ammeter, and assuming by 'low' it was showing discharge when idling with lights, heater, and wipers on.
confused-gif.gif
yea - a lot of assumtions.

Wipers, Headlights, and heater fan probably draws around 25-29 amps.
We all know that maxes out the typical roundback at idle speeds. So that would be normal.

I've been trying to get him to look at the presumed ammeter with no accessories on, both at idle and 1250 rpm. That combined with the voltage measurement will give an idea if things are normal or not.

Dana67Dart said:
13.5 at RPM, battery is charging.
Click to expand...
If the battery is low it will charge. The only way to know if it is charging is to look at the ammeter.
wink-gif.gif

Your point probably is 13.5 Volts is within normal regulator operating range and that is true!


upload_2020-4-27_16-38-24.png
 
Last edited:
Just did some testing on my dart.
All test measurements were at battery
Key off all acc off
12.57 at battery
Engine idleing all acc off
14.16v
Engine at high RPM all acc off
14.16v ( initially went higher but settled in there)
Engine idleing, headlights, wipers and heater motor on high
12.5v
Engine at high rpm, headlights, wipers, and heater motor on
14v

I don't think you have a problem.
 
I had that problem with a 68 charger and a 67 dart gt. They had tried everything. I put a new batteries in them with a higher cranking amp rating. Cured both cars. Our cars have a big amp draw that needs higher rated amperage. U will have better ell electrical performance all around. In this case bigger is better. A weak assed batter is our major down fall. Kim
 
Crappy low rpm performance of the factory alternators is where the issue lies. The low RPM needs more output than the alternator can provide. The bigger battery solution is a stop gap to the real issue.
 
You must log in or register to reply here.
-

Back
Top