Low charge to no charge issue pulling hair out

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. Is that ok or not ok thats the first change of signal from what battery had
1.5v voltage drop. Is excessive. Even my 0.4 is more than I would like.

Path...

Battery to headlights

From the battery to the starter relay
From relay to fusable link
From fusable link to bulkhead
From bulkhead to main splice
From main splice to ignition switch
From ignition switch to dimmer switch
From dinner switch to bulkhead connectors
From bulkhead connector to headlight bulb ( might be another connector along the way)

Battery to alternator

From the battery to the starter relay
From relay to fusable link
From fusable link to bulkhead
From bulkhead to main splice
From main splice to the ammeter
Through the ammeter
From other side of ammeter to the bulkhead
From the bulkhead to the alternator post.

A quick test would be to get a proper jumper wire and bypass the ammeter.

If the voltage drop goes down you could part or all the problem.
 
Im thinking my ammeter is the culprit
I have purchased several gauge clusters for their gauges

Several of the ammeter's posts were loose and one was twisted to the point it was shorted.
 
Next i checked the red connected post at back of ammeter and the result was 10.30
I don't have my wiring diagram available right now but if the red goes to the battery that would suggest the bulkhead terminals themselves
 
Will do some more digging on Saturday with these extra suggestions thanks a bunch this is helping me narrow this down
 
Fyi i just got the car so trying to work the kinks, the dimmer switch i believe is shot as well needing replacement
 
11.64 positive battery terminal


Alternator batt post 10.30
So that's 1.3 Volt drop between the battery and mains splice with around 10 -12 amps flowing through.
1.2 V/12 amps = .1 ohms
Similar to the resistance we saw before with 20 amps charging.
That tells us most of the resistance is in the battery circuit, and not the run from the alternate to the mainsplice.

As far as I know, the '73 Barracuda charge circuit is the same basic layout as we've been discussing. There are some variations when a car came with heavy duty wiring for certain options such as heated rear defrost.

With headlights on, the current path looks like this.
1732851079606.png


I would check for ground losses first.
Then check the battery connections and wires in the engine compartment since they are easiest to access and see.
All it would take is a bad battery cable or a quicky replacement battery terminal clamp to cause resistance like that.

The bulkhead connector teminals are relatively small and exposed to engine heat, along with moisture, so they too are possible culprits. Or it could be a little resistance at each junction. You can keep doing voltage drop checks to narrow it down or just start checking all the connections.

The ammeter itself is typically a metal plate with a pressed in studs. The needle moves by magnetic deflection when a current runs through the plate.
It's possible the studs have become loose, but that's very rare unless they get overheated. More common is the ring terminals on the wires get overheated(from overcharging or a short) or get oxidized and corrroded from a water leak. Generally its pretty protected in there compared to the wires and connections from the battery to the firewall, and hte battery to ground.
 
So i just did some extra tests. I disconnected the ammeter wires and married them together turned lights on and same result, 1 point drop 11.7 to 10.4 so from the interior bulkhead connector all the way to the back of the alternator. I checked all the other junctions in photo above except headlight switch and ignition switch.

Something odd however when i was hooked up normal i had 9.8 to battery side of fuse block with lights on where as the bulkhead and ammeter matched at 10.4 all from 11.7

So what i know is battery to bulkhead engine compartment side goes to 11.7.

Red wire on ammeter and firewall interior side bulk head is 10.4

And rear battery “red wire side of fuse block is 9.8.

Whats dors all this tell me for narrowing
 
You could run a heavy jumper from batt positive and tie it the married ammeter wires that will bypass the bulkhead connector.

Then you could do the same from batt positive to alt post.

You can leave all the other OEM wiring in place.

Basically you are bypassing the bulkhead terminals to/from the battery and From the alternator.

If your voltage drop goes away you know the resistance is in the bulkhead connectors.


Btw use caution as this setup also bypasses the fusable link. So no protection to the cars wiring
 
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Just did it, 12.13 to start then after 3 minutes with highbeams on multimeter shows 11.87
Okeh. A fully-charged "12 volt" battery, once the surface charge is skimmed off by running the lights for 3 minutes, should show 12.6v. I was wondering if you were going to see something like mid-high 10s, which would indicate a dead/dying cell in the battery, which could cause the symptoms you're seeing. But no, this what you've measured tells us all six cells are at least more-or-less alive. Other battery tests (such as your drop-after-charge results) might still point at a battery problem, but I don't think it's causing your poor-charge symptoms.
 
You could run a heavy jumper from batt positive and tie it the married ammeter wires that will bypass the bulkhead connector.
Then you could do the same from batt positive to alt post.

[…]

Btw use caution as this setup also bypasses the fusable link. So no protection to the cars wiring
If you want to make that bypass permanent/safe, see here.
 
And/or the wiring harness "main weld" where a bunch of wires come together behind the dashboard
The main splice is on the black alternator side of the ammeter

OP is getting voltage drop on the red Battery side of the ammeter
 
JB I think you are overthinking and missing something. I recommend you start cold and think about this

Think about the sections of the problem in simpler terms and where the problem could be

1...The RED the ammeter and BLACK ammeter circuit along with bulkhead connector for those two wires, in which voltage drop can affect (2) below

2...The ignition "run" circuit which feeds the VR power, and the alternator field blue power wire. This also constitutes the sensing for the VR which is why ignition harness voltage drop (eliminating it) is so very important in Mopars. This of course also includes one more bulkhead connector terminal for the "run" ignition power

3...The charge path back to the battery from the alternator, however unless really bad, some drop from alternator stud (under charging load) from there to the BLACK bulkhead terminal may not be so bad

4...Something internal in the alternator wrong, not limited to, but including partially open or shorted stator and or diodes, partially shorted or intermitted field, and bad contact with the brushes and field.

5...Bad VR. These of course are solid state and can develop some interesting problems. Do not discount something simple like a bad connection in the VR connector, which can be difficult to "notice."

6....Defective battery. Batteries as well can develop weirdness, including sulfation If you have a known good battery out of another "rig" do not be afraid to drop it in, even temporarily in such cases
 
A healthy alternator, with the VR bypassed and with a good battery that is nearly charged, should be able to ramp up system voltage--depending on engine RPM to dangerous levels. DO NOT DISCOUNT something REALLY basic like a pulley that is polished up from slipping and therefore almost impossible NOT to slip

In other words, after starting, running ?? a minute or two to get the battery back "up" from starting, if you remove green wire and ground that alternator terminal, if that doesn't work, leave that field terminal grounded, then remove the blue field wire, and jumper power to the last field terminal direct from, say, the starter relay stud, then manually raising engine RPM, system voltage should climb right up and I would be careful to hold it below 15.5--16 at most. if it will not do that, concentrate on

dead or defective battery
Measure drop between alternator output and battery
Highly suspect alternator
or the mentioned belt/ pulley / tension slip etc.
 
Okeh. A fully-charged "12 volt" battery, once the surface charge is skimmed off by running the lights for 3 minutes, should show 12.6v. I was wondering if you were going to see something like mid-high 10s, which would indicate a dead/dying cell in the battery, which could cause the symptoms you're seeing. But no, this what you've measured tells us all six cells are at least more-or-less alive. Other battery tests (such as your drop-after-charge results) might still point at a battery problem, but I don't think it's causing your poor-charge symptoms.
I do think I have an issue with my battery though. It’s only a 2024 but the previous owner didn’t use the vehicle much so I don’t believe especially with this charging problem and not using it enough. I’m unable to keep a charge at 12 V overnight it drops in the high 11’s. So I’m kind of thinking it’s a lot of things. I do think I need a new battery because it’s not able to reach above 12.2 and stay there for more than 30 minutes after a charge to drop 11.9. I’m wondering if I do have a battery that’s 12.6 if it does charge into the 13’s and everything is good. I do have a voltage drop though regardless
 
I think you made this more difficult than you needed to.
But lets go through it because its a good way to learn.

I disconnected the ammeter wires and married them together turned lights on and same result, 1 point drop 11.7 to 10.4 so from the interior bulkhead connector all the way to the back of the alternator.
1. You proved the the ammeter had nothing to do with the voltage drop.
(Lets call voltage differences voltage. Points can mean a number of things and get confusing.
Voltage is energy level. A change in voltage represents electrical energy getting converted to something else.)

The only way voltage can drop in this scenario is when electrons flow through resistance.
-> The electrons are not flowing to the back of the alternator when you flip the headlights on.
-> When measuring at the bat terminal with the alternator off, the alternator output wire is an extention of the multimeter probe. 10.4 Volts at the alternator BAT terminal means the voltage at the main splice is 10.4 Volts.

1732887428969.png



Something odd however when i was hooked up normal i had 9.8 to battery side of fuse block with lights on where as the bulkhead and ammeter matched at 10.4 all from 11.7
You are correct.
This shows additional resistance between the ammeter terminals and the point you measured in the fuse block.
But we know that the main splice was also 10.4 Volts under the same condition, so this resistance is either in the Q3 wire or more likely right at the fusebox.
In fact this is all pointing toward a little bit of resistance throughout the main circuits. It very well may be worth taking the time to remove and clean all of the connections, starting with the battery cables, but including the bulkhead, fuse box, steering column connector, and engine connector if used in '73.
1732888064040.png

Power to the headlights goes through wire L1 to terminal B1 on the headlight switch. There is a circuit breaker in the switch.
Power for the parking, tail, and marker lights first goes through the fuse box, then to terminal B2 on the headlight switch.
Also if you had the door open, power to the dome light goes through the fuse box.

So what i know is battery to bulkhead engine compartment side goes to 11.7.
Are you sure?
Did you back probe the bulkhead?
Did you check at the stud on the starter relay?
The locations most likely to be compromised by heat, moisture, and strains are in the engine bay. Overcharging can damage the fusible link and its connectors because its only 16 gage wire. In fact it should be the first thing damaged by too much current.

Have you made any direct voltage measurents?
Battery to Alternator stud (main splice) direct measurement will reveal if the 1.3 volt drop with lights on is entirely in the wiring, or if a portion is in the grounding or battery ground wires. Put the red probe on the battery positive and the black probe on the alternator stud.
Red wire on ammeter and firewall interior side bulk head is 10.4
OK
And rear battery “red wire side of fuse block is 9.8.
Chrysler calls the feed to the always hot side of the fuse block Q3.
Q is the designation for all power feeds to items not needed to run the engine. AKA 'Accessories"

Do a search here on removing and cleaning bulkhead connectors. Personally I like Deoxit, a soft brush and a small fiber brush used in electoronics for cleaning.
The fuse terminals are a bit more difficult but sometimes really neccessory to clean.

The battery terminals can be cleaned with a wire brush or some fine emory cloth.

The Battery
In my opinion 11.7 V with the lights on is poor. 12.3 V with nothing on is a low charge state.
The fact that the voltage drifted down after remvoing from the charger could be the surface charge disapating. Or if the battery was hooked up to the car system, it could indicate something it on and drawing a small amount of current.

It seems that sometimes these small automatic chargers can not truly figure the battery state or condition. Thats why I ask what the voltage was when the charger was attached. As long as the charge is offering power at more than 13 volts, preferably closer to 14 Volts, the battery should be either charging or maintaining the charge. The battery itself should not be getting hot as long as the charge rate is 5 amps or less.

If its a standard battery, check the acid level. The plates should be covered in fluid. If not add distilled water to the cells that are low.
You can also check a battery charge with a hydrometer type checker if its a battery where the caps can be removed.

I agree that its new enough that there is a good chance it can be revived.
 
I just had to swap the battery out of my 67 Barracuda because it wouldn't restart after a long trip back home. There had been clues for a while although I didn't put it all together until it had insufficient juice to turn the starter.

After getting a jump start I brought the car to my garage, shut it it off and measured battery with the key on start.
Voltage dropped to 5. The battery is shot.
I put it on the little charger and after a few minutes it decided that the battery didn't need charging, just 'conditioning'.
1732890874982.png

Sorry. This is wrong. The acid is probably cooked out or no longer exchanging ions or such. Can't complain - its from 2008.

Checking a different Optima that I hadn't traded in it, but was dying after about 4 years of use.
The charger correctly diagnosed this battery as low on charge. It also thinks the voltage is 11.4 but my multimeter says its lower than that.
1732890597910.png



When doing a voltage check on a new battery 12.7 to 12.8 Volts is about what we'ld expect at 60 ot 70*F
I'd consider 12.5 to 12.6 as marginal.

But as discussed earlier, immediadely after charging there will be a surface charge. can't go by that. The surface charge voltage goes away slowly over time or quickly if a load is placed on the battery (such as turning on a light). It does not represent any significant amount of stored energy.


This photo essay with an old school charger shows how a voltage and current relate when charging
 
JB I think you are overthinking and missing something. I recommend you start cold and think about this

Think about the sections of the problem in simpler terms and where the problem could be

1...The RED the ammeter and BLACK ammeter circuit along with bulkhead connector for those two wires, in which voltage drop can affect (2) below

2...The ignition "run" circuit which feeds the VR power, and the alternator field blue power wire. This also constitutes the sensing for the VR which is why ignition harness voltage drop (eliminating it) is so very important in Mopars. This of course also includes one more bulkhead connector terminal for the "run" ignition power

3...The charge path back to the battery from the alternator, however unless really bad, some drop from alternator stud (under charging load) from there to the BLACK bulkhead terminal may not be so bad

4...Something internal in the alternator wrong, not limited to, but including partially open or shorted stator and or diodes, partially shorted or intermitted field, and bad contact with the brushes and field.

5...Bad VR. These of course are solid state and can develop some interesting problems. Do not discount something simple like a bad connection in the VR connector, which can be difficult to "notice."

6....Defective battery. Batteries as well can develop weirdness, including sulfation If you have a known good battery out of another "rig" do not be afraid to drop it in, even temporarily in such cases
These are great points will change battery as well from another car and see if it continues i didn't check the run wire in bulkhead will look at that too the connector to VR seems good and tight
 
1732892435084.png


The ammeter is scaled 40 amps Discharge to 40 amps Charging. About 12 amps discharge is what we see in your photoand thats about right for headlights and all exterior lamps on.
 
@Mattax thank you for all this info it really helps me put this together. Based on your large reply i do believe something is up with battery alone. The charger say 100 percent at it finishes at 12.2 then drops, under multiple circumstances i cant get the battery to stay in 12’s at any point. So very well the battery may have cell damage from lack of use by previous owner etc.

I will be deep diving into all this first thing tomorrow. I used wire brush and some 120 grit to sand away the green corrosion on the red male terminal and it had full continuity so the cleaning helped that terminal as 3/4 of terminal was reporting back current but the bottom quarter of terminal wasnt giving feedback until i sanded away brushed away the connection clean. Oddly enough it didnt change any details or make them better below i added the details of my assignment from you to see where im at and where to look next before i tear apart the entire fuse block. Let me know where i need to focus on finding the loss now. Static is just the way the car sits with everything connected the other is the light drop test info you walked me through with each of the Tested point values.

IMG_1796.jpeg


IMG_1797.jpeg
 
A healthy alternator, with the VR bypassed and with a good battery that is nearly charged, should be able to ramp up system voltage--depending on engine RPM to dangerous levels. DO NOT DISCOUNT something REALLY basic like a pulley that is polished up from slipping and therefore almost impossible NOT to slip

In other words, after starting, running ?? a minute or two to get the battery back "up" from starting, if you remove green wire and ground that alternator terminal, if that doesn't work, leave that field terminal grounded, then remove the blue field wire, and jumper power to the last field terminal direct from, say, the starter relay stud, then manually raising engine RPM, system voltage should climb right up and I would be careful to hold it below 15.5--16 at most. if it will not do that, concentrate on

dead or defective battery
Measure drop between alternator output and battery
Highly suspect alternator
or the mentioned belt/ pulley / tension slip etc.
So i did exact this to start and jumped green field wire and alternator kicked on and started charging the battery and was at 13.87 successful which told me the alternator is working
 
@67Dart273 now im in the weeds looking at drops and all sorts of crap i didnt know i had which im glad i found a 1 volt drop somewhere inside my dash/fuse block the witch hunt continues
 
JB your inbox is full. I wanted to exchange phone no's
Del
 
Let me know where i need to focus on finding the loss now.
Well this part is easy thanks to your additional measurements. Look at where the resistance occurs with current flowing through.
1732904584291.png


Disconnect the bulkhead connector. Then remove the terminal from each half and clean them.

Based on your large reply i do believe something is up with battery alone. The charger say 100 percent at it finishes at 12.2 then drops, under multiple circumstances i cant get the battery to stay in 12’s at any point. So very well the battery may have cell damage from lack of use by previous owner etc.
I threw a lot of information at you to help you understand how the battery charges.
Finishing at 12.2 Volts is not right. The charger should be at 12.8 Volts or even better at 13.+ for the battery to get fully charged.
When a good battery is fully charged, its surface charge will be a little over 13 Volts and no measureable current (electrons) will be seen going into the battery.
So at this point I don't know if its the charger is incapable or the battery is damaged.

The fact that the battery was drawing 20 amps from the alternator when the engine was running suggests to me this battery probably can be recharged. If its a flooded battery with removeable caps then you can check the condition further.
It works like this. The amount of power drawn for recharge depends on both the battery's charge state and the voltage of the recharge.
Have you ever noticed that lights run brighter when the alternator is running than when power is coming from the battery?

Same idea with the battery recharge. If a battery recharging at 12.5 Volts is drawing 20 amps, then if it was given recharge at 14 volts it would draw 30 or 40 amps. That much current will (a) damage connections and wires, and cause the battery acid to bubble and cook off (or worse).

to sand away the green corrosion on the red male terminal and it had full continuity so the cleaning helped that terminal as 3/4 of terminal was reporting back current
"reporting back current"
You may be confusing current and voltage.
Current is electrons moving. Voltage is electrons looking to move.

An analogy can be made to pressurized air or water system.
Voltage is pressure created by the compressor or held in an air tank.
Current is the amount of air flowing in the system.

but the bottom quarter of terminal wasnt giving feedback until i sanded away brushed away the connection clean.
The visible corrosion further reinforcing my suspicions.
Check the ground terminal too.
 
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