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1 wire alternator confusion
#1
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humanpotatohybrid
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I have a Delco Remy "1 wire" alternator on my car with 2 spade connectors in the back that I think are unlabeled. I have a couple questions:

- Do these even charge at idle? Do you have to rev the engine a bit to get them going, or do they never charge at idle?

- I have read that the #1 terminal goes to a charging light connected to ignition, other times I've read that it goes straight to ignition to power the field windings. Is there a way to tell which is correct?

- Likewise for the #2 terminal, some say to jump it to the output for voltage sensing, others say it's redundant. Does it matter?

This is the only pic I have right now.

Attach file:



jpg  20221109_060527.jpg (1,070.08 KB)
225076_6391e9b6be830.jpg 4032X3024 px

Posted on: 12/8 8:42
'55 400. Needs aesthetic parts put back on, and electrical system sorted.
'55 Clipper Deluxe. Engine is stuck-ish.
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Re: 1 wire alternator confusion
#2
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BigKev
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Are you sure it's a 1-wire?

Sounds like a standard GM SI Alternator to me. Aka 3 wire.

The large stud goes to the battery. One of the terminals goes to the dash light and then to ignition power.

The other terminal is the sensor/exciter, which most people loop over to the bat stud on the alternator, but really should go to the main junction on the battery harness.

You can look at my project blog, as that's what I have in my car.

Posted on: 12/8 9:08
-BigKev


1954 Packard Clipper Deluxe Touring Sedan -> Registry | Project Blog

1937 Packard 115-C Convertible Coupe -> Registry | Project Blog
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Re: 1 wire alternator confusion
#3
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humanpotatohybrid
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Yeah that's what I was thinking. Aren't they called 1 wire because they only need one wire? (The idiot light and reference signal, what you were describing, should be both optional, right?)

Posted on: 12/8 9:15
'55 400. Needs aesthetic parts put back on, and electrical system sorted.
'55 Clipper Deluxe. Engine is stuck-ish.
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Re: 1 wire alternator confusion
#4
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Cli55er
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Posted on: 12/8 10:07
1937 Packard 138-CD Deluxe Touring Limousine
Maroon/Black 1090-1021
[url=http://packardinfo.com/xoops/html/modules/registry/View.php?ID=232]1955 Packard
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Re: 1 wire alternator confusion
#5
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BigKev
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Generally, a 1-wire (which I have in the Jackard) is just the battery stud. No other terminals.

If it has the other terminals, it is a 3-wire (One Bat stud and two terminals).

A 3-wire won't charge unless it is "excited".


This may help:

https://www.streetmusclemag.com/news/alternators-1-vs-3-wire-with-painless-performance-and-ron-francis/

Posted on: 12/8 10:29
-BigKev


1954 Packard Clipper Deluxe Touring Sedan -> Registry | Project Blog

1937 Packard 115-C Convertible Coupe -> Registry | Project Blog
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Re: 1 wire alternator confusion
#6
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humanpotatohybrid
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How much do you need to rev the engine to excite the generator? I charged the battery with an external charger overnight so it should be good to drive to the shop today and back in a couple days (10 min drive) hopefully. If I can find something at an auto parts store I'll wire in an idiot light to terminal 1 before I drive it more. Seems to be hard to find incandescent ones though.

Posted on: 12/8 11:07
'55 400. Needs aesthetic parts put back on, and electrical system sorted.
'55 Clipper Deluxe. Engine is stuck-ish.
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Re: 1 wire alternator confusion
#7
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BigKev
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It's that voltage-sensing terminal that needs to be connected back to a 12v source. Usually, people make a small pigtail and just reconnect it back to the BAT terminal on the Alt.

If it still isn't charging after that, and you give it a rev or two, then it's probably a bad alternator (ie internal regulator shot).

Posted on: 12/8 11:55
-BigKev


1954 Packard Clipper Deluxe Touring Sedan -> Registry | Project Blog

1937 Packard 115-C Convertible Coupe -> Registry | Project Blog
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Re: 1 wire alternator confusion
#8
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DavidPackard
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Humanpotatohybrid:

I did a ‘deep dive’ on this subject about 15 years ago. Give me a few hours to find the binder that has all on the details.

Your comment about having to ‘rev the engine’ to get it to charge is suggesting that the alternator has internal components that would require the #1 to be connected to power source current limited to approximately 1 ampere. The indicator bulb is the means to provide both current limiting and a means to indicate everything is OK. There were GM cars that used small indicator bulbs and a parallel resistor to achieve the correct excitation current. All of that detail was under the dash, not internal to the alternator.

Give me a few hours.

dp

Posted on: 12/8 12:38
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Re: 1 wire alternator confusion
#9
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humanpotatohybrid
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Thanks Dave, awaiting your reply

Posted on: 12/8 13:33
'55 400. Needs aesthetic parts put back on, and electrical system sorted.
'55 Clipper Deluxe. Engine is stuck-ish.
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Re: 1 wire alternator confusion
#10
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DavidPackard
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Humanpotatohybrid:

I found the binder!

Just a bit of background: I converted my Model A from 6 to 12 volts. The previous owner had installed a Delco 10-SI alternator equipped with internals to regulate at 7.2 volts (aka 6 V), positive ground. My conversion was to 12 volt negative ground, with a Delco 10-SI alternator. The car was initially wired with one wire connected to the B+ terminal (that’s the big one), with the other two terminals covered with a rubber plug. As far as I know that alternator had no objectionable characteristics, so I wired the 12 volt alternator exactly as the previous. That alternator had what I considered an objectionable characteristic of ‘late cut-in’. Since the Model A has a ridiculously low idle speed and a rather small crank pulley diameter, both of the alternators were fitted with the smallest diameter pulleys available.

The small terminals should be identified on the casting, but if not the number 1 terminal is closer to the B+ terminal. Terminal 1 appears somewhat of a ground when the alternator is ‘off-line’ and will transition to output voltage when the alternator is ‘on-line’. The plot thickens a bit because Delco has many internal regulators . . . voltages of 6, 12, and 24, and both ‘one-wire’ and ‘three-wire’ configurations, terminals 1 & 2 connected, and a few regulators that have only one of the small terminals.

The Delco manual is quite clear that the rotor is excited by the current applied to terminal #1. My testing on the Model A was guided by a circuit in a shop manual for an Oldsmobile where a 10 ohm resistor was in parallel with a low candle power indicator lamp. From that I assumed that the target current flow to terminal 1 should be about 1 amp. I actually tested 0, 0.25, 0.50, 0.75, and 1.0 amps (50, 25, 16.7, and 12.5 ohm resistance), in conjunction with a LED indicator (trivial current flow). The cut-in speed was definitely reduced each time the terminal 1 current was increased. For quite a long time I had the 1 amp configuration mounted in a plastic project box, with the LED indicator, and an ON/OFF switch. I would start the car, and then a bit later after turn the excitation ON, which excited the rotor and the alternator transitioned to ‘on-line’ smartly.

Let’s move on to terminal 2. That’s the terminal that I understand what the purpose is, but I’ve actually run with nothing connected to it, which has me baffled. The Delco information identifies this as the remote sense terminal, meaning if a wire is connected from a specific location in the car’s electrical system to terminal 2, then the voltage at that specific location will equal the regulated voltage, and the output as measured at terminal B+ will likely have a higher voltage. At the Saturday night car shows I’ve frequently seen short jumper wires from terminal 2 to the B+ terminal. I have dated circuit diagrams for the voltage regulators, so there may be an up-dated version that uses the Zener alone if terminal 2 falls below a certain level.

In summary we have both run Delco 10-SI alternators without the two small terminals connected, and other than late cut-in the alternators seem to have worked just fine. Later I modified the car’s electrical system by connecting terminal 2 to a location much closer to the battery, and connecting terminal 1 to a power source that was current limited to approximately 1 ampere. In that configuration the alternator seem to work just fine, and the late cut-in speed had been adjusted closer to the engine’s idle speed.

If it was my car I would connect terminal 1 to a key activated circuit that is current limited to 1 ampere, and then connect terminal 2 to either the B+ terminal or the main binding post of the wiring harness (likely the battery side of the solenoid).

Now on to a bit of speculation on my part. I’m thinking of an engineering meeting at Delco when the failure modes and effects were being discussed, and the subject of what should happen if the indicator bulb fails. It seems that having a late ‘cut-in’ was an acceptable effect. Moving on to the robustness of the design if the customer didn’t need the remote sense feature. I think the regulator was design to allow the customer decide whether that feature was necessary.
I’m looking at a Delco illustrated parts catalog and see both 6 volt, 12 volt, and 24 volt regulators that are identified as ‘one-wire’, and they have both small terminals. There are also regulators that have terminal 1 and terminal 2 connected with a ‘bridge’ that can be cut in the field if remote sense is desired. There are also regulators that have only one of the small terminals. I have not found in the Delco catalog a 10/12-SI regulator without the small terminals.

For those members that have installed Delco 10-SI or 12-SI alternators, and use the car regularly, I would use the three-wire design . . . only because that design was used by GM for many years. They’re available at a reasonable price at a typical ‘big-box’ auto parts store, and if the clocking is not correct that can easily be changed without removing the pulley. Clocking refers to the location, aft looking forward, of the small terminals with respect to the threaded mounting hole.

To ‘Big Kev’s question about whether the alternator is a ‘1 wire’: If the only short coming is a late cut-in speed I would presume the alternator is a ‘3-wire’. The link to the red & white wire connector that Cli55er provided was the one that I used, but it was from the local auto parts store. I somewhat take exception to the comment that 3-wire alternators won’t charge if connected as a 1-wire. My experience suggests the 3-wire does work when only the B+ terminal is connected, but the cut-in speed is objectionably high (excited by only residual magnetism). And given the infinite combination of pulley diameters and final drive ratios the alternator may never ‘cut-in’, which would lead to a conclusion that would be correct for that car, but not all cars.

What is the diameter of the alternator pulley? I’ll presume that the Packard doesn’t have quite the octave range as say a SBC.

dp

Posted on: 12/8 16:58
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