Alternator Troubles! 1973 Plymouth duster 318
Long Answers and follow up steps.
Battery: 10 volts with the starter turning is acceptable. 10 Volts in run - which is very low load - is not.
Try this
a. Measure battery voltage with key off, door shut (dome light off), nothing on.
b. Measure battery voltage with low load such as dome light light on, then add loads such as parking lights and then headlights.
Normally a fully charged battery will have a potential of 12.5 to 12.8 Volts
Add a small load and it will drop just a little.
If the battery is low, and it has enough acid (assuming removable tops) so you can see the level, put the battery on a charger. If its a manually control charger, charge it at a low rate. 2 amps would be OK.
Field Circuit:
Here is what is happening when you observe the voltage is the same at two locations.
Voltage goes down only when the electricity does work. When there is no resistance, there is no work. Also when the electrons are not moving, there is no work.
[A small aside here, it always pays to take a look at the ammeter to help complete the picture. The ammeter will reveal if the electrons are moving to or from the battery. ]
As you know from the "Alternator ID" thread the blue and green field wires are connected through the rotor. A continuity test will just show they are connected. With the key off, a resistance check will give some indication of whether there is short or not.
With the key in run and the battery as source of power, the voltage regulator will be read system voltage as low. [The regulator wants system voltage to be around 14 to 14.9 V ] Therefore the regulator should be internally connecting the green wire to ground.
But if the green wire is not connected, or the regulator is not working or well grounded, then the circuit will be open and no current will flow. No flow = no work = no loss of energy level (voltage)
If its 10 Volts everywhere in the main circuits that are connected, no current is flowing.
Graphically, no connection to ground, everything on the battery side is at the same voltage.
Only when and where the electrons move through a device, a resistor, or a poor connection do they lose energy.
Going through the rotor most of the energy becomes and electromagnetic field.
If they are moving through a resistor or poor connection, then the energy is all given off as just heat.
Back to your situation.
Check that the voltage regulator is well attached to the body, and the battery has a body ground on the negative terminal.
Check the green wire is intact back to the regulator. You could do this with key off, remove the connector at the regulator and the green one on the alt. Then do a continuity test of the green wire
If you test with the key in run, see if the ammeter needle moves slightly toward discharge. No movement of the needle, then there are no electrons moving. it shouldn't move a lot, but with ignition switch on run, it should show flow to ignition ECU, coil, the alternator field, and maybe an electric choke assist or carb solenoid. 5 to 6 amps.
Long Answers and follow up steps.
Battery: 10 volts with the starter turning is acceptable. 10 Volts in run - which is very low load - is not.
Try this
a. Measure battery voltage with key off, door shut (dome light off), nothing on.
b. Measure battery voltage with low load such as dome light light on, then add loads such as parking lights and then headlights.
Normally a fully charged battery will have a potential of 12.5 to 12.8 Volts
Add a small load and it will drop just a little.
If the battery is low, and it has enough acid (assuming removable tops) so you can see the level, put the battery on a charger. If its a manually control charger, charge it at a low rate. 2 amps would be OK.
Field Circuit:
Here is what is happening when you observe the voltage is the same at two locations.
Voltage goes down only when the electricity does work. When there is no resistance, there is no work. Also when the electrons are not moving, there is no work.
[A small aside here, it always pays to take a look at the ammeter to help complete the picture. The ammeter will reveal if the electrons are moving to or from the battery. ]
As you know from the "Alternator ID" thread the blue and green field wires are connected through the rotor. A continuity test will just show they are connected. With the key off, a resistance check will give some indication of whether there is short or not.
With the key in run and the battery as source of power, the voltage regulator will be read system voltage as low. [The regulator wants system voltage to be around 14 to 14.9 V ] Therefore the regulator should be internally connecting the green wire to ground.
But if the green wire is not connected, or the regulator is not working or well grounded, then the circuit will be open and no current will flow. No flow = no work = no loss of energy level (voltage)
If its 10 Volts everywhere in the main circuits that are connected, no current is flowing.
Graphically, no connection to ground, everything on the battery side is at the same voltage.
Only when and where the electrons move through a device, a resistor, or a poor connection do they lose energy.
Going through the rotor most of the energy becomes and electromagnetic field.
If they are moving through a resistor or poor connection, then the energy is all given off as just heat.
Back to your situation.
Check that the voltage regulator is well attached to the body, and the battery has a body ground on the negative terminal.
Check the green wire is intact back to the regulator. You could do this with key off, remove the connector at the regulator and the green one on the alt. Then do a continuity test of the green wire
If you test with the key in run, see if the ammeter needle moves slightly toward discharge. No movement of the needle, then there are no electrons moving. it shouldn't move a lot, but with ignition switch on run, it should show flow to ignition ECU, coil, the alternator field, and maybe an electric choke assist or carb solenoid. 5 to 6 amps.