Ammerter be gone-wiring question?

[PlasticBoob]

Thanks for the explanation, it cleared up some things, but I still can't make the final leap...

Are there any situations where the alternator can go haywire and start overcharging and pumping out vast amounts of amperage? Say if the voltage regulator breaks? I had a situation with an original-style parts store voltage regulator that was overcharging, say near 16-17 volts. Was it also not putting out excessive amperage because the voltage shown was just potential? Maybe I do need an ammeter, eh? My temporary fix in that situation was to turn on the heater blower and some accessories to bring it back down to around 14 volts.

What would be the reason for putting a circuit breaker on the alternator's BAT output, in conjunction with a fusible link on the main feed wire to the cab (#12 or #55)? Is the breaker then redundant?

[nograin]

I can answer the first one quick. The other I have to look at the diagram so that will have to wait.

Thanks for the explanation, it cleared up some things, but I still can't make the final leap...

Are there any situations where the alternator can go haywire and start overcharging and pumping out vast amounts of amperage? Say if the voltage regulator breaks?

Yes, voltage regulators can fail in full field mode. That's fancy shorthand for saying the internal switch is closed (like putting a jumper across it). This allows as much electricity through the rotor windings as its wants. The output voltage will rise to whatever the alternator is capable. Some equipment will run better. Higher voltage means less current is needed for the same power. Other equipment will have problems as the high voltage can jump or break though air gaps and breakdown some components. The battery may try to accept more charging and inside may get hot, boiling off liquid.

I don't know about the circuitry in the SI regulator. Old school external ones are like the points types. Regulation is done by switching the power feed through resistance, no feed, and no resistance positions.

I had a situation with an original-style parts store voltage regulator that was overcharging, say near 16-17 volts. Was it also not putting out excessive amperage because the voltage shown was just potential? Maybe I do need an ammeter, eh? My temporary fix in that situation was to turn on the heater blower and some accessories to bring it back down to around 14 volts.

Good temporary 'fix'. The battery will draw more. Here's a link showing the charging voltage and current relationship in a series of photos (my jeep). I'll put a series of pictures somewhere more convenient soon or later. Notice when the battery was drawing more than I wanted, reducing the voltage also reduced the current.

https://www.forabodiesonly.com/mopar/threads/alternator-amp-rating.396944/#post-1971969715

[nograin]

What would be the reason for putting a circuit breaker on the alternator's BAT output, in conjunction with a fusible link on the main feed wire to the cab (#12 or #55)? Is the breaker then redundant?

Lets Looks at a factory system where something like that was done.
With wiring all distribution from the starter relay or solenoid, in 1986 the factory installed a fusible link between the alternator and the battery. This protects the alternator circuit from the battery.

Every wire coming off the distribution point is protected with a fusible link, greens or yellow in the diagram.


With the earlier wiring design, there is only one wire from the battery to the main distribution point. For that reason, only one fusible link was needed. A breaker or link on the alternator output might provide a little additional protection for the few seconds the motor kept running. And a breaker might kill the the motor faster or stop it when the ground fault was intermittant. If the short to ground makes good contact, all current will flow there as its the path of least resistance. That's why they assume the engine will stop and of course the alternator will too. Think back to the member who had a wire with bad insulation behind the dash. That's exactly what happened, engine stopped running. Being fused it was instant.

Then there was one with the mouse nest? I'm pretty it kept running only because the fusible link was replaced with a solid wire.

[nograin]

Maybe I do need an ammeter, eh?

Ammeter can be quite helpful.
A good moparts thread about that here.
The questions are whether its worth it to send it out for repair? is there a plow, winch or other items that will draw lots of current through the charging wires every time they are used?
I think the answers are: maybe if you really like to see whats going on. No unless you do something clever such as a relay and wire to directly charge the battery when accessories are used. No if the alternator struggles to keep up at idle with the A/C or othe equipment on.
Anyone with an '86 and later vehicle would have to add one that was calibrated for an external shunt. You have to really want one to go through that effort.