Low charge to no charge issue pulling hair out
I think you made this more difficult than you needed to.
But lets go through it because its a good way to learn.
(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.
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.
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.
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.
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 think you made this more difficult than you needed to.
But lets go through it because its a good way to learn.
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.
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.
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.
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.
OK
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.