Ammeter Bypass / Charging Question

[Gerald Morris]

I was rebuilt by local guys that have a great reputation. I believe it is original to the car.

They might have used a heavier stator than original spec. Rebuilders do this, especially independent shops who rely on a good local reputation to keep business. Try measuring its high current output with full voltage to the field. Is this a 60A alternator? Don't be surprised to see 72-80 amps output from it if its originally an OEM 60A unit.

 

[furious70]

Aside from some weird theoretical massive capacity alternator where even milliseconds of charging was too much there is no practical point where an alternator can't be properly governed to the correct voltage.

In a properly functioning system you could swap from a 40a to a 100a alternator and exactly nothing would change for example.

 

[fury fan]

Sunday night my daughter noticed that my volt gauge in the 68 NYer bounced around some on the way home from the grandparents. When we got home I put my meter on the battery and it was getting 14.8 volts.

Yesterday I was going to drive it to work when about 2 miles from home I noticed the gauge bounce radically, for instance from 10 - 16 volts, I don't know exactly. This is with one of FURYGT's regulators. I turned around and took it home. When I got last night I put another one of FURYGT's regulators on it. At first idling in the driveway I got 14.5. I went for a 20 minute drive to Wal-Mart and checked it there and I was at about 14.7.

Having yet another of FURYGT's regulators that was brand new I put it on this morning and drove it to work, 16 miles - 25 minutes. Almost watching the gauge more than the road, yikes... There was some movement in the gauge, but I saw no radical movement. Pulled it into the shop and put meter on it right away. This brand new regulator is putting out 14.9 volts.

So - before the voltmeter needle wiggling - what did your voltmeter normally show?
Was it 14.5+ before the needle was wiggling?

 

[Gerald Morris]

Aside from some weird theoretical massive capacity alternator where even milliseconds of charging was too much there is no practical point where an alternator can't be properly governed to the correct voltage.

In a properly functioning system you could swap from a 40a to a 100a alternator and exactly nothing would change for example.

Nothing will change so long as that little caveat about "properly functioning" is in force. Should something draw on an oversized alt without adequate sized main conductors, then you can watch a piece of skimpy 12 gauge SLOWLY start acting as a "fusible link", especially if the malfunction doesn't blow its proper overcurrent protector. Low voltage systems do this **** you know. Under a heavy load such as a cold weather ice storm at night let's say, (headlights+heater blower+other accessories....) that old crap will all pull heavily without blowing anything, and a big alt will burn the main feed to the battery/ammeter up before ANYTHING pops or trips. Best to be careful. Motors especially can draw current out of phase with voltage, even DC motors, and that adds to the mischief with crude old switch breakers.

 

[furious70]

People continue to give poor advice about all this. A 40a alternator is more than powerful enough to burn the wiring out with a shorted connection or device on the circuit.
Separately, There is no technically sound reason to suggest here that a too large alternator is causing the charging at too high of a voltage as measured at the battery.

 

[Gerald Morris]

People continue to give poor advice about all this. A 40a alternator is more than powerful enough to burn the wiring out with a shorted connection or device on the circuit.
Separately, There is no technically sound reason to suggest here that a too large alternator is causing the charging at too high of a voltage as measured at the battery.

Then if the SUSPECT ALTERNATOR isn't producing the excess voltage, which ceased to show when replaced by another alternator,, then sources such as Democrats, fairy dust, or other, more rational candidates MUST BE AT WORK! We can throw V=IR out the window, while tooling down the road with the heater, high beams, a kilowatt audio amp and refrigerator for our beer all run off a 12 gauge wire now fed by a 130A Tuff Stuff alternator, all in PERFECT CONFIDENCE that the odd smell of oxidizing vinyls wafting into the heater duct is in FACT, mere senescent, ossified brain cells burning out, which, having no other use, won't be missed.

 

[furious70]

You keep confusing amperage for voltage. Just because you have that problem doesn't mean there natural world behaves that way.
An alternator only does what the regulator tells it to unless it's stuck open.
Even then, a 40a alternator is more than capable of more than 14.7v if it's internally faulty.
You claimed in post #21 that somehow an alternator with more amperage capacity (and assumption here) correctly working could somehow provide too much voltage.

That's simply not possible.

Nobody should read this post and think that installing a correctly functioning 60a or 80a alternator could in any way cause an over voltage condition.

In this case the old alternator either had a malfunction or something in the sensing circuit was fixed unintentionally when doing the r&r.

 

[furious70]

Back to actually taking about this car, if it were mine I would have been measuring voltage all over the car to see what was happening

 

[fury fan]

I dunno. Y'all lost me at Democrats.