Electrical gremlin

[67Dart273]

"Damn near every electron in that car flows thru the ammeter" Doesn't matter if it comes from the alternator or the battery.

This is true. If EG the car is shut off and you have the headlights, whatever, powered on, all the current is coming from the battery. If the car is operating "normally" cruising down the road, then pretty much everything comes from the alternator

 

[Mattax]

Lessee.....The ammeter only shows charge/discharge. Agreed. What discharges said battery?
Every electrical function in the car, save the alternator. Thus, what I said is true. In order for the ammeter to function at all, "Damn near every electron in that car flows thru the ammeter" Doesn't matter if it comes from the alternator or the battery.

Proof?

Disconnect either side of the ammeter and leave it hang (insulated from ground, natch). Tell me what still works.....

Actually, some people do the equivalepnt of that to test the alternator. They disconnect the battery and if the car keeps running -and often it does, the pronounce the alternator good. Its not actually a good test, and additionally can cause problems, but the point is the battery is not needed once the car is running.

If you ever have worked with manual start engines, and I'm sure you have, you'll notice they run just fine on the magneto. Same idea.

So to your first question. "What discharges said battery?"
The battery discharges whenever it is connected to a complete circuit AND its the power source with the highest voltage.
So in practical terms.
The battery discharges during starting, recharges after starting, and does pretty much nothing until its time to restart the engine.
Occassionally the battery will help out at idle when the electrical loads exceed what the alternator can provide at 14 Volts.
The battery is at best capable of providing power at 12.8 Volts.

The proof is shown on the ammeter. When you are driving, what does the ammeter show? After the battery is charged, it shows no current flowing in or out.

Now lets look at the current flowing through the ammeter at start.
Its 3 to 5 amps. Just enough to deflect the ammeter a little.
That current goes to the ignition and the starter relay.
The power to the solenoid splits off at the relay.
Power flowing through the starter goes direct through the heavy cable to the starter.

Once the engine has started, the alternator's rotor can get powered up. From that point on, power flows from the alternator to whatever circuits are closed. Some goes to the battery until its recharged. We can measure 14 volts in the power lines because of the alternator.
Power is supplied from the power source with the highest voltage.

On a typical setup the wiring which sees the highest loads is from alternator to the main splice. It carries all of the current to run the things the operator turned on, plus whatever is demanding for recharge. Running the heater fan, headlights, wipers, can add 25 to 30 amps. That current doesn't show up on the ammeter.
Why?
Because its not going through the ammeter.

Bottom line. Once the battery is recharged, no current flows through the ammeter as lon gas the alternator can provide power.
Normal driving, the current flow looks lilke this.

 

[Mattax]

This is true. If EG the car is shut off and you have the headlights, whatever, powered on, all the current is coming from the battery. If the car is operating "normally" cruising down the road, then pretty much everything comes from the alternator

So just to be clear, how does everything go through the ammeter if its coming from the alternator?

 

[jos51700]

So just to be clear, how does everything go through the ammeter if its coming from the alternator?

I'm not pulling diagrams but Ithought about it and think you are, SOMEWHAT correct for stock cars, and I think I know where I went wrong

In MY car, all the current flows through the ammeter if it's hooked up, because I bypassed the bulkhead with my charging wire.

It's been some 20 years or so since I did it, and now i don't remember!

I gotta keep thinking on this. I'm also thinking, "don't these cars die if the fusible link goes?"
If so, that would back my original position, but I also know a field issue on the alternator will smoke every light in the car. It's been too long.

 

[AJ/FormS]

In this map, you can see that the headlight switch gets it's power directly from the #1 splice, on the alternator side of the ammeter but before the ignition switch. That means that you can use the headlight switch as a diagnostic tool.
Like this;
If when your system crashes, the headlights still work, then the problem lies AFTER the #1 splice, towards the ignition sw.
But if the headlights quit too, then you gotta work backwards to the battery. And as you can see, there are only three items in the path; the ammeter, the bulkhead, and the F-link. Well, 4 if you include the binding post on the starter-relay.
The bulkhead connector is a known trouble-spot.
On my car I just punched a hole thru the connector and cut the metal bits off; then soldered a heavy gauge insulated wire across the ends. That was like two decades ago, and never had a problem since.
Yes you can replace the the F-link with a big fuse; but that defeats the purpose of the F-link which is to endure short-term overloads. The fuse will just blow; and you better have a handful of them in the car at all times for diagnostic purposes.
As for the ammeter; notice the studs have a nut on either side if the connecting wires. Be sure you don't overtighten the outside nut without anchoring the inside nut, cuz if the post twists, you can bet the ammeter is close to being junk. Also; check out what is behind the cluster face, where the ammeter resides. In My car, the pedal bracketry is right there, and if I'm not careful, the always-hot ammeter wires can easily contact that metalchit with predictable results; always disconnect the battery when fiddling with the ammeter.

 

[RustyRatRod]

I clicked on this expecting to see an electric powered race Gremlin. I'm sorrily disappointed.