350 voltage question

scremineagle · Post by **scremineagle** » Wed Mar 25, 2015 5:24 am

Thanks for all reply's on alternator change over. I do have 14 volts at ammeter so needle on gauge most likely just not working. But i am having trouble energizing alt. My original plug in wires show 12.8 volts when i turn on the key but when you start machine they drop to 10.8 & alternator won't energize. would this change in voltage be normal or is something drawing too many volts i.e. possibly the starter or maybe its something to do with the original regulator? Only place i seem to be able to energize is at the starter which is'nt switchable. Thanks

Post by **Lavoy** » Wed Mar 25, 2015 10:19 am

I assume you mean voltmeter shows 14 volts? If so, that is about right, regulator will typically kick in at 14.2-16.2 volts.
Lavoy

scremineagle · Post by **scremineagle** » Wed Mar 25, 2015 5:21 pm

I got the new alternator energized with switchable power but had to hook other wire to main lug on starter to send charge back to the battery. I have 14.8 volts on both sides of the ammeter but the gauge does'nt even wiggle. I tried a new ammeter gauge same result. Any clue as to why the gauge does'nt work. Maybe not enuff volts? I'm confused should have been an easy change over. If anyone has a clue would much appreciate the help.

Post by **Lavoy** » Wed Mar 25, 2015 6:34 pm

Ammeter measures current, not voltage. If you don't have any load like lights, etc, it won't read much on a charged battery. If battery is low enough that it should be showing charge, might be wired wrong.
Lavoy

kilohertz · Post by **kilohertz** » Tue Mar 31, 2015 9:36 am

Run down your battery a little with some lights or even just crank it without letting it start. Then when it starts you should see it swing to the right, indicating charge current going into the battery. You will see the same voltage on both sides of the ammeter, as it is shunted with a very low resistance. 14.8VDC is what I see on mine as well. I think mine energized just fine with 10-11 volts on the field wire. There will also be the .7 volt drop across the diode.

Stan Disbrow · Post by **Stan Disbrow** » Tue Mar 31, 2015 11:03 am

Hi,

All you need is a voltmeter on the battery terminals to troubleshoot.

A new 12v battery at rest with a full charge will read between 12.5 and 12.9 volts. It ought to drop to 9 volts when cranking. Once it starts, the voltage will rise. If you have 14.8 volts at the battery with it running, it is charging.

The dash ammeter is between the battery and the rest of the machine, save the starter. It should, as already noted, show a discharge current with lights on and not running. It should show a charge current just after starting. With a new battery, that won't last long as a new battery will recover quickly. And, then the needle will center again.

With it running, turn the lights on and the ammeter needle will do a quick wiggle to discharge and back to center. That is the battery feeding the lights until the voltage regulator kicks up the fields in the alternator.

With it running, the float voltage should be between 13.8 and 14.5 volts. But seeing 14.8 might be a meter that is reading a few tenths off. I have one I keep in the tractor shed which reads a full volt high. A cheap flea market PoS, but one which I won't cry over should I leave it lying atop the track as I pull out.

Stan

Edit: a crawler is not nice to a meter left lying atop the track....

That could be my new tag line....

kilohertz · Post by **kilohertz** » Tue Mar 31, 2015 11:50 am

Stan Disbrow wrote:
Edit: a crawler is not nice to a meter left lying atop the track....

That could be my new tag line....

Nor is it kind to sunglasses as we found out when we loaded my 440IC.

Scottyb · Post by **Scottyb** » Tue Mar 31, 2015 11:51 am

Chainsaws left on the tracks do not last long I have learned as well.

I am going to print this thread and put it into my service binder, every time I have an charging problem I have to re learn the concepts.

Scott

Stan Disbrow · Post by **Stan Disbrow** » Tue Mar 31, 2015 1:17 pm

Hi,

Well, then. I may as well add some things.

Battery: an antiquated chemically based tank of electrons. For us, lead and zinc plates in a plastic box with sulfuric acid. The electrons are all on the negative side, and move thru the wiring to the positive side. When the electron pressure equalizes, then it is dead. And, then the sulfuric acid can get busy eating the lead and zinc. This, usually the condition found when one jumps onto the crawler to actually do some work.

Jumper cables: what one needs shortly after jumping onto the crawler. This requires a not-dead battery in something else fairly close by. Which rarely happens. So, we then need a.....

Battery charger: an AC transformer with diodes to make the AC into DC. Usually found with corroded clamps due to the sulfuric acid in the battery. Because we got smart and left it connected.

Generator: a form of battery charger spun by the engine. Usually found with bad brushes and a worn commutator on the armature. This means the battery doesn't charge when running. So, see Jumper Cables and Battery Charger.

Alternator: an Alternative to a Generator, but that is not where the name comes from. Some smart guy named Tesla figured out one can get more power from Alternating current than some guy named Edison could from Direct Current, and send it over long distance at high voltage and then step it down when it gets there via a Transformer.

So, some other smart guy whose name we can't remember figured he'd skip all the wire between the power plant and the transformer in the battery charger and stick the Alternating Current Generator onto our machines directly. Oh, and the name Alternator comes from everyone getting tired of saying the long name.

But now, we have three phases of AC and six diodes which the Generator does not have to go bad. More often than the commutator and brushes do in the generator. And, if just one of the diodes shorts rather than opens, it puts a lot of AC out to kill the transistors in the Regulator.

Regulator: used to be a couple coils and resistors and contacts in a big can one could open up and figure out why the generator was not charging the battery. Then, it became a transistorized circuit in an aluminum heat sink filled with tar. So much for troubleshooting. These days, it is inside the alternator so we don't have to t-shoot anything beyond replacing the alternator. And the battery.

Ammeter: measures amps between the battery and everything else. Except the starter. It is not big enough to handle starter current. It is actually pretty useless these days of cheap digital voltmeters. The old generators were low current and slow to charge, and extra lights might overload the charging. So an ammeter was handy. These days, with all the extra current from an alternator, the battery voltage rises so fast, you cant really see it. And, extra lights are no problem.

Voltmeter: the main troubleshooting tool. Look at the battery voltage to begin with. See how far it drops when starting. See how quickly it rises once started. See where it stabilizes. Tells you everything. Until you leave it on a track and pull out of the barn. Did I mention they are cheap these days?

So, there it is. The basics from a bored electrical engineer.

Stan

kilohertz · Post by **kilohertz** » Tue Mar 31, 2015 2:28 pm

And don't forget, before you start troubleshooting, there is a skill testing question....what color is the green ground wire?

Stan Disbrow · Post by **Stan Disbrow** » Tue Mar 31, 2015 3:04 pm

Hi,

Ground is Black on DC systems, of course. Now, wait for it. This is true on both positive and negative ground.

Then someone thought they'd have a laugh and make black hot on single phase AC systems

And then someone else added Green for Ground and hooked it to the same point the White wire hooks to!

And, then Single Phase AC is actually Two Phase when you look at the center tapped transformer. But, they still want to call it Single Phase.

So, I use my Single Phase as Dual Phase and hook it up to Three Phase motors. So, there!

Stan

jtrichard · Post by **jtrichard** » Tue Mar 31, 2015 8:38 pm

Single phase also know as split phase correct? and the color of the Green wire is Copper unless it is tinned OR that crap that NEVER be used in small sizes aluminum

NWJD fan · Post by **NWJD fan** » Tue Mar 31, 2015 11:03 pm

So now we have generators, alternators, regulators, ammeters, voltmeters, DC, AC, rectifiers even, maybe! all messing around with volts, amps, watts and maybe ohms. What are these units about? They are somewhat similar to water moving through a hose. Volts are the electrical pressure that makes the electrons move through the wire. Higher voltage is like higher psi pushing water through a hose. Amps are the number of electrons moving through the wire, kind of like the volume (gallons) of water moving through a hose. Watts are an expression of power which has the potential to do work. Voltsxamps= watts. X volume of water being pushed by Y amount of pressure has the potential to create Z amount of power which can be expressed as watts. Anybody heard of hydro electricity? 746 watts (I think) = 1 horsepower. Ohms are electrical resistance which slows those electrons down reducing voltage down stream of the resistance. Every inch of wire of a given size has some fraction of an ohm of resistance. Larger wire has less resistance than smaller wire so the further you need to move a fixed amount of electrons at a fixed voltage the larger size of wire you will require. If you are pumping a given volume of water at a constant input pressure a larger hose will move that water further than a smaller hose due to less friction loss (resistance). Confused? So am I. Maybe Stan will take on Ohms law

kilohertz · Post by **kilohertz** » Tue Mar 31, 2015 11:44 pm

Well....you knew it was coming...with many of us here 50+ annums....you may remember your electrical/physics teacher passing this one out...

The Sex Life of an Electron

by Eddie Currents*

One night when his charge was pretty high, Mirco-Farad decided to seek
out a cute little coil to help his discharge.

He picked up Milli-Amp and took her for a ride in his Megacycle. They
rode across the Wheatstone Bridge and stopped by a Magnetic field with
flowing currents and frolicked in the sine waves.

Micro-Farad, attracted by Milli-Amp's characteristic curves, soon had
her fully charged and proceeded to excite her resistance to a minimum.
He gently laid her at ground potential, raised her frequency, and
lowered her reluctance.

With a quick arc, he pulled out his high voltage probe and inserted it
in her socket, connecting them in parallel. He slowly began short
circuiting her resistance shunt while quickly raising her thermal
conductance level to mill-spec. Fully excited, Milli-Amp mumbled
"OHM...OHM...OHM!"

With his tube operating well into class C, and her field vibrating
with his current flow, a corona formed which instantly caused her
shunt to overheat just at the point when Micro-Farad rapidly
discharged and drained off every electron into her grid.

They fluxed all night trying various connectors and sockets until his
magnet had a soft core and lost all of its field strength.

Afterwards, Milli-Amp tried self-induction and damaged her solenoids,
and, with his battery fully discharged, Micro-Farad was unable to
excite his field. Not ready to be quiescent, they spent the rest of
the evening reversing polarity and blowing each others fuses.

As was mentioned earlier, this will be a thread to print for future reference.

Stan Disbrow · Post by **Stan Disbrow** » Wed Apr 01, 2015 5:17 am

Hi,

Lord help us all in this hijacked thread! I will mention, but not explain, for us over 50 electrical folks, about the rhyme we were taught to remember the resistor color code. It is no longer politically correct.....

Ohm's law is simple. One amp of current will flow at one volt through one ohm of resistance. And, one watt of power, which is voltage multiplied by current.

How about the old AC vs DC example of ping pong balls thru a pipe? Fill the pipe with balls to represent the electrons in the wire. Stuff in another ball, one pops out the other end. Repeat. This is DC. All the electrons have to move the one way. Now, push in one extra ball until the one at the other end almost falls out, then push it backwards. Back and forth. This is AC.

Note, though that the stopping and starting of the electrons means a loss of power for AC given the same voltage and current. The factor is 70.7 percent, and is called RMS, which we sometimes see mentioned. Most often with audio power amplifiers, oddly enough.

Now, to re-track the thread somewhat.

Now, when we move electrons thru a wire, there is a magnetic field produced. Which is why there are field coils in generators and alternators. The regulator pushes more or less into the field coils as it sees the need for more or less output from the generator.

An AC field is better than a DC field when it comes to this, which is why alternators put out more amps from a smaller unit than a generator.

Stan

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