Alternator and Voltage Regulator Questions

[Mattax]

The main thing is to reduce or improve the connections, especially on the power supply circuit.
That, and use an alternator that will supply the power needs of your car at idle.

Power supply circuit is from the alternator to the main junction (a welded splice) when the alternator is doing its job.
Power supply is from the battery to the main splice when the engine is off or being started.

Simplified diagram; On a car with ignition switch in the column, there's another connector.

 

[ScamperTom]

The main thing is to reduce or improve the connections, especially on the power supply circuit.
That, and use an alternator that will supply the power needs of your car at idle.

Power supply circuit is from the alternator to the main junction (a welded splice) when the alternator is doing its job.
Power supply is from the battery to the main splice when the engine is off or being started.

Simplified diagram; On a car with ignition switch in the column, there's another connector.
View attachment 1715215132

I see, so looping the black and red wires at the ammeter in effect makes a parallel power supply circuit running from the battery to the junction at all times. Why not just cut and cap one of the wires instead of running them in parallel? Not ideal to have a hot flapping in the breeze?

 

[Mattax]

I see, so looping the black and red wires at the ammeter in effect makes a parallel power supply circuit running from the battery to the junction at all times. Why not just cut and cap one of the wires instead of running them in parallel? Not ideal to have a hot flapping in the breeze?

By looping do you mean connecting the black and red wires at the ammeter with a jumper? That would make a parallel path to the ammeter. If for some reason you want the ammeter out of the circuit, place the ring terminals of the black and red wires onto the same stud.

If the wiring from the battery to the main splice is cut, the engine can't be started and the battery won't recharge.
See if these flow diagrams help.
Current flow in Charging Systems with Ammeter:

 

[67Dart273]

Yes, either the MAD mod, or just jumpering a wire from alternator to battery or starter relay, does two things

CAVEAT..........the jumper wire leaves you without fuse link protection unless you provide one

First, since the charge current is now going through the jumper to the battery, that extra current is relieved through the body wiring.

Since the body loads, such as heater, lights, ignition, etc, is now the only current going through the bulkhead, the big black and the big red effectively become paralleled. This helps tremendously

HOWEVER the above does NOT "fix" bad connections in the bulkhead connector, or other connectors such as the headlight/ headlight switch, ignition switch or connector etc, etc

 

[67Dart273]

I often refer to "functional path" but bear in mind current actually goes from neg to pos.

But the "functional path" originally was centered at the welded splice

If the engine was stopped, the functional path was from battery....fuse link....through the bulkhead connector........through the ammeter.......to the welded splice.........and branch off to ignition switch/ accessory hot buss, / headlights etc

If the engine was running and charging, the path was from alternator.......through the bulkhead...........to the welded splice........and off to the loads as above........through the ammeter........through the bulkhead connector.........and to the battery (if / when charging)

EVERY SINGLE POINT mentioned above is a potential for voltage drop if they are diminished, including the welded splice which is rare BUT they HAVE failed!!!

 

[ScamperTom]

Thanks y'all!

By looping do you mean connecting the black and red wires at the ammeter with a jumper? That would make a parallel path to the ammeter.

By looping I meant the MAD ammeter bypass. I can't really see the ammeter as is and I have an aftermarket voltmeter, so I don't need it.

Yes, either the MAD mod, or just jumpering a wire from alternator to battery or starter relay, does two things

CAVEAT..........the jumper wire leaves you without fuse link protection unless you provide one

First, since the charge current is now going through the jumper to the battery, that extra current is relieved through the body wiring.

Since the body loads, such as heater, lights, ignition, etc, is now the only current going through the bulkhead, the big black and the big red effectively become paralleled. This helps tremendously

I did add a maxi fuse to the jumper going from the alternator to the battery. I think that should give adequate protection, although slantsixdan recommends a fuse at each end of the line.

EVERY SINGLE POINT mentioned above is a potential for voltage drop if they are diminished, including the welded splice which is rare BUT they HAVE failed!!!

I am going to clean and grease all of the connections I can reach. I will also have to check for voltage drop through the bulkhead. I assume that anything more than 1-2 volts is unacceptable?

What I'm dealing with:

 

[Mattax]

By looping I meant the MAD ammeter bypass. I can't really see the ammeter as is and I have an aftermarket voltmeter, so I don't need it.

If you don't want the ammeter, just bypass it. Simplest way is to put both ring terminals onto one of the ammeter studs. (Just make sure the stud isn't loose.)
MAD's loop puts all of the current to run the car through the 16 gage fusible link. There's no reason to do that.

 

[67Dart273]

If you don't want the ammeter, just bypass it. Simplest way is to put both ring terminals onto one of the ammeter studs. (Just make sure the stud isn't loose.)
MAD's loop puts all of the current to run the car through the 16 gage fusible link. There's no reason to do that.

Doing this does NOTHING to help the weak wiring and weak bulkhead connector terminals. And that is NOT what the MAD modification does.

The MAD mod electrically makes the original RED feed wire to the ammeter and the original BLACK ammeter/ alternator wire IN PARALLEL to feed the interior. That ALSO removes CHARGING CURRENT from those two conductors, lessening the load on them

If you run a big wire direct from battery to alternator that will help BUT it defeats the fuse link and leaves some of that big wiring UNPROTECTED without an additional breaker/ fuse /link

 

[Mattax]

It makes them feed in parallel, but feeds them both through two small fusible links that are in series. It trades a short path direct path with a weak connection for a longer path with two choke points. Better to directly run a power supply wire from the alternator to the main junction seperate from the one going to the battery.

 

[Mattax]

This would be a better way to have a direct charging wire.
Downstream of the battery is still protected by the fusible links.
Power from the alternator goes direct to the main junction.

 

[4spdragtop]

Watching....trying to learn too lol

 

[Mattax]

To learn how the power flows put your finger on the highest voltage souce and trace the path of least resistance to the equipment that wants that power.
If there are two paths with somewhat similar resistance (or lack of it really), the current will be roughly be divided between the two paths.

In the above diagram with the purple arrows, the scenario is battery charged, engine running.
-> Power comes from the alternator's output stud at 14.2 Volts.
-> Find the shortest path with least resistant to the ignition, fusebox, or headlights.
Then take your finger, or a colored pencil, and do the same on the next diagram.

You can then try other scenarios, such as :
. engine running and recharging battery
. engine starting (hint, battery at approx 12.5 Volts will be the source of power)
. engine running on battery (no power from alternator)

 

[ScamperTom]

This would be a better way to have a direct charging wire.
Downstream of the battery is still protected by the fusible links.
Power from the alternator goes direct to the main junction.

View attachment 1715218572

This makes sense that you get power straight from the alternator via a low resistance path. But what if the charging jumper blew? Wouldn’t all the power be redirected through the bulkhead and main junction, exactly where we didn’t want it?

Doesn’t it make more sense to run a new, fused, heavy wire straight to the battery, then redo the wires leading to the junction so that there’s only one fusible link (choke point) instead of two? That would cut down on resistance while ensuring that the alternator’s output never gets routed through the bulkhead.

 

[Mattax]

This makes sense that you get power straight from the alternator via a low resistance path. But what if the charging jumper blew? Wouldn’t all the power be redirected through the bulkhead and main junction, exactly where we didn’t want it?

Yes.....
If the direct charging wire broke, all of the power to run the engine would continue to flow through the bulkhead to the main junction, and from there to the igntition etc.
The only difference would be the addition of the power to recharge the battery. On a non-modified car, that's not an issue. It would be the same as stock except instead of some sort of bulkhead connection, there would be a splice. A well done splice will have less resistance than the stock terminal connections used on most years and models.
.. and no
we still need it to go through the firewall to the main junction. The goal is to do that with minimal resistance for the expected current.
In both diagrams above, the intention was to show the wires are going directly through the firewall, say by drilling a hole through the original bulkhead connector or using a grommet.

Doesn’t it make more sense to run a new, fused, heavy wire straight to the battery, then redo the wires leading to the junction so that there’s only one fusible link (choke point) instead of two? That would cut down on resistance while ensuring that the alternator’s output never gets routed through the bulkhead.

The battery only supplies power while starting and when the alternator can't supply enough.
Fusible links are there to protect against battery discharge to ground while allowing temporary high but expect current loads.
The disadvantage of a fuse on the charging wire is that it can be blown by a spike in current. Recharging a really drained battery can pull 20 plus amps for a short period of time. Yes you can use a fuse with a heavier wire, say 8 gage. That's probably OK, but we really don't want a 40 or 50 amp fuse on a 12 gage wire.

As mentioned above, unless the system is being entirely redesigned, there's no way around sending power through the firewall to the main junction. However a good way to reduce the amount of power flowing in through the bulkhead and all of the connections afterwards is relays. Heavy loads can be powered direct from the alternator tri using fused circuits and relays triggered by the original switches.
In my experience the headlight circuit is the most lightly wired on A-bodies and putting the lamps onto relays does the most good. (The factory wires to the lamps are just 18 gage, at least for most years.)

 

[ScamperTom]

Yes.....
If the direct charging wire broke, all of the power to run the engine would continue to flow through the bulkhead to the main junction, and from there to the igntition etc.
The only difference would be the addition of the power to recharge the battery. On a non-modified car, that's not an issue. It would be the same as stock except instead of some sort of bulkhead connection, there would be a splice. A well done splice will have less resistance than the stock terminal connections used on most years and models.
.. and no
we still need it to go through the firewall to the main junction. The goal is to do that with minimal resistance for the expected current.
In both diagrams above, the intention was to show the wires are going directly through the firewall, say by drilling a hole through the original bulkhead connector or using a grommet.


The battery only supplies power while starting and when the alternator can't supply enough.
Fusible links are there to protect against battery discharge to ground while allowing temporary high but expect current loads.
The disadvantage of a fuse on the charging wire is that it can be blown by a spike in current. Recharging a really drained battery can pull 20 plus amps for a short period of time. Yes you can use a fuse with a heavier wire, say 8 gage. That's probably OK, but we really don't want a 40 or 50 amp fuse on a 12 gage wire.

As mentioned above, unless the system is being entirely redesigned, there's no way around sending power through the firewall to the main junction. However a good way to reduce the amount of power flowing in through the bulkhead and all of the connections afterwards is relays. Heavy loads can be powered direct from the alternator tri using fused circuits and relays triggered by the original switches.
In my experience the headlight circuit is the most lightly wired on A-bodies and putting the lamps onto relays does the most good. (The factory wires to the lamps are just 18 gage, at least for most years.)

Using relays to keep the current down definitely seems like a good idea. I see you’re right tho, the power to run the car at least has to go through the junction. It still seems ideal (on a modified car) to keep the charging current on a different path however. Still, you’re right that does mean more work than just adding a jumper to the battery.

 

[Mattax]

Yup. With additional electric equipment the charging wire may have to do more. Whatever is done needs to be thought out.
For example with EFI, it probably makes sense to power from a fuse or breaker box off of the alternator. After all, it only runs when the engine is running. But during start up its adding a lot more load through the charge wire - which during start is the power supply wire. In turn, that means the battery recharging after start will draw more current if the alternator can supply it. Furthermore, if the new demands are higher than the wire and link can handle without resistance, there will be voltage drop and the EFI and pump may or may not tolerate that.
A different situation is a truck with an electric winch. Most alternators won't have the power to run a winch - it has to be hooked to the battery side. This is the type of situation that probably got the truck ammeter shown on MAD's website so hot the plastic distorted - high electric demands on the battery side of the gage both from the winch and then to recharge a low battery.

PS. IMO a drop of 1 to 2 Volts is way too much. Something in the order of 0.1 to 0.2 Volts would be acceptable. IIRC, that's about all the factory considered acceptable in they're advice to techs. ( It's in one of the MTSC's about diagnosing electric)