Technical Another alternator thread

I run a voltage sensing setup on my 49 Buick and it works flawlessly. On my tractor I use a one wire alternator, which they were designed for, it also works flawlessly. Do you see the difference?

 

Is this multiple choice ?
Good thing we never use parts from other sources that weren't "designed " for our cars !

 

I struggle with wiring a bit, so I go with what I know. My harness kit came with a variety of charging system options, I went with the 3-wire one.

I keep the instructions in a binder with my post-it crib notes stapled in plus an excel generated from-to wire list.

 

I'll spell it out. The tractor has a very simple electrical system. It has 2 single beam headlights, one dash light, and a single element tail light, plus power for the coil. The alternator is less than 3 feet from all the electrical needs except for the tail light.
The Buick with the voltage sensing wiring has a complicated electrical system. It has power windows, halogen headlights, 2 tail lights, 2 horns, multiple dash lights, air conditioning, electric door and trunk poppers, HEI ignition, electronic cruised control, and a backup camera. Plus the car is almost 17 feet long, so the electrical load is quite a ways from the alternator. This is why a load sensing setup works much better for a car than a single wire alternator as used on the tractor. Using parts from other sources is traditional, we just have to be smart enough to use parts that are designed for the correct application.

 

I have found that having a cheap "laminator" and a box of laminating sheets makes it very handy to save things you might want to save for later reference. I use it for things I want to hang on the shop walls near the welder or electrical quick reference in a car,............whatever I'm likely to forget and need a reference for.

Seems like I been laminating a lot more stuff lately............

 

I should do that. I have things like torque specs that I look at quite a bit it seems. I have some of the book in those plastic sleeves, but laminating is more better.

 

Get a "3 hole punch" too. I have a lot of stuff I put in binders for quick reference. Even have all my "important papers" laminated and in a binder for my heirs............

 

Chinese 1 wire, you can hear it roll on, no voltmeter..AAA card

 

This isn't quite true. A 1 wire alternator regulator will monitor voltage at the output terminal (or close to it) of the alternator, not the voltage at the battery . However, it will put out current based on load, it's not a constant rate. Add accessories or load and the alternator automatically compensates, it doesn't matter where it is sensing voltage.

You can prove this by measuring current at the output wire of the alternator. Start the engine and let the current stabilize. With no accessories on the current should be pretty low, probably less than 10 amps. Now turn on the lights, blower and other accessory loads. You will see the current go up to match the load. Depending on the load, voltage may drop slightly, it depends on what the alternator is capable of handling.

The perceived problem with a 1 wire alternator is that it isn't really sensing true battery voltage and could potentially overcharge a battery. In reality the voltage at the alternator is very close to the voltage at the battery. The output wire from the alternator is probably an 8 or 10 gauge wire and it probably connects to the starter terminal. The wire from the starter terminal to the battery is probably a -0 or larger. There is very little voltage drop from the battery to the alternator. The 1 wire alternator on my 64 Chevy truck has probably been on there for over 15 years (I've had the truck for 13 years). In that period I have replaced 1 battery. The old truck is my daily driver.

 

Actually, it's more likely that you'll undercharge the battery with a one-wire. Voltage drop is the main issue with our 12V systems. As an example, let's say that under load the alternator is outputting 13.4V at the alternator terminal. Add in a 2.5% drop at the connection at the battery, your now down to about 13V. Add in another 2.5% between the battery connection and the fuse panel, now it's about 12.7V. Add another 2.5% drop in an individual branch circuit such as headlights, now your down to 12.4V and things like dim lights start showing up. And a 2.5% drop is conservative, drops in the 3 to 5% range are common.

The amount of voltage drop has nothing to do with the system voltage. It's strictly controlled by the load in amps, wire size and length. Extend a wire an extra 2-3 feet, you'll see more drop. The problem is with only 12 volts, any loss has an outsized effect on the total as a percentage.

Because a three-wire alternator measures voltage upstream from the alternator (usually at the fuse panel or ignition switch), that initial .7 volt drop at the panel is now gone, ensuring that branch circuit loads will have a better shot at working right. This will increase voltage at the battery, so overcharging is a small concern, but the OEMs have been doing this since the first 'modern' charging systems showed up in the late 40s.

 

I do that, less the laminating. I just backed everything up onto an external hard drive, getting ready to get a new PC. I have a binder with all my OT car receipts. The one on my Ford I salvaged from work, it is pretty well stuffed.

 

Yes, the external hard drives are pretty compact these days. I have one that I downloaded pretty much all the reference info and other car and airplane info that I have accumulated over the years. Then I disconnect it so it hopefully doesn't get any virus. Hate to think I would ever lose all that info.

 

I am surprised that the Zone did not have a one wire in stock. That is an extremely common alternator.

I have run one wires forever. I have a shelf full of them in different states of repair. Some chrome, some painted, some crusty. I even bought one new at an auction last year for $2.50, got it home and discovered that it is 6 volt positive. I probably will not ever use it but no one else has one. LOL

I am going against my normal way of doing things on my current project. Everything under the hood is 1965 including the alternator and external regulator. I called several parts stores in a 4 state area and they all had parts in stock, regulators, brushes and alternators. So I figure I am good.

 

I’v been following this thread very closely

I don’t get the knock on single wire alternators, I like the simplicity

I can understand using too small of a wire to and from the alternator can cause issues and maybe having the regulator mounted away from the engine it will stay cooler.
but
As far as seeing the load, I don’t get the difference where the regulator sits is in the circuit
Like the battery the regulator sits in parallel with the loads which are all in parallel

My single wire in my Tbird is rated at 100 amps, has been working fine for 7 years

Need a better explanation

 

Broke down to its most basic form, a three-wire will compensate for voltage drop between where the power is produced (alternator) and where it's distributed for use (fuse panel). It has zero to do with load other than how that load affects voltage drop. A one-wire doesn't, end of story. Whether that drop is a problem or not depends on multiple variables and can only be determined by checking for voltage drops or if problems occur. A one-wire can work, but not as well in most cases. That's the reason why the OEMs use three-wire alternators in cars; if a one-wire would work and meet their engineering standards, you could bet your last dollar they'd use 'em for the cost savings of two less wires times millions of harnesses produced every year.

 

So let me see if I understand this
If you take a one wire alternator and add the pigtail as shown in the diagram it now becomes a three wire?
I’m a little slow so forgive me if I got this wrong

 

That's half of it. The #2 terminal is the sensing wire, and rather than being connected to the alternator output, you extend this wire to either your fuse panel or ignition switch. It should be connected to unswitched power; remember, it's just a 'sense' wire, no real power flows through it.

The white wire is for a warning light. If no warning light is used, it needs to be connected to the ACC terminal at the switch, or if connected to the IGN terminal, install a diode to prevent backfeed and not have the motor shut off with the key.

If you have a 'true' one-wire, you won't have those terminals and will need to replace the regulator with a three-wire type.

 

I too am a masochist.

If the truck in question is your avatar, IIRC that generation from the factory used an ampmeter.
I don't know how, where, or how accurate the voltage gauge used is.

Never stated nor implied that.
You asked for a reason, I gave you three.
It wasn't an invitation for debate, just answering your question.

Although the '12V' system does run a bit more than at 12V, it really shouldn't be pushing past 14.2V.
It simply will damage the battery. If the regulator is not actively monitoring and compensating then it can overcharge as well as undercharge.
Verify that your battery is fully charged and holds charge(12.6V).
Verify battery cells are full.
Verify cells are equally charged using a hydrometer.
14.7V is just too high of voltage for a fully charged battery or a battery being charged for an extended time. Over voltage, when the battery is fully charged, will just overheat and damage the battery. This will reduce the life of the battery.

As you will note I stated...

Didn't state battery, said '(itself)' i.e. alternator.

As Steve pointed out, it depends on how the alternator is built.
There are three basic types of S.I. type alternators in the aftermarket.

• 3 wire stock type alternator, needs a switched 'excite' circuit to activate, uses a 'sense' circuit to properly monitor/charge the system, and has a BAT terminal for charging.
• 1 or 3 wire alternator. Can be used in place of the stock 3 wire but functions as a 1W alternator. Often the #1 and #2 terminals are bonded together. These tend to have a factory preset voltage output with no readily way to adjust output voltage. This is the 'typical' 1 wire alternator readily found. It is not a 3 wire at all outside of visually appearing to be so. It is a basic 1 wire alternator.
  
• 1 wire alternator, regulator does not have the #1 and #2 terminals. Usually a rubber plug in place of the terminals. Voltage can be adjusted 13.5-18V for desired output. These are usually considered 'RACE' alternators, and should only be installed in a vehicle where load conditions are consistent and warranted.

 

Mike, mine has the rubber plug covering two male spade connectors. What does that make it.

On the voltage, the multi-meter I was using showed the 14.73. The Volt meter attached to the switched on power reads 14V, slightly less occasionally..

Appreciate your observations

Ben

 

I picked up a 2TB drive at Best Buy for $62. I keep it unplugged if I'm not using it. Best Buy offers to load my existing PC stuff to a new one, but who knows what demons are lurking in some of that stuff?