A call for help to the electrical specialists.

[henryford30]

Hello Specialists


I bought my 30' Ford last year. At that time, the vehicle had already been converted to 12 volts.
Now I wanted to replace the 1 wire alternator with a 3 wire alternator.
I had the problem that the charging current could not be measured, the multimeter showed me some values, but no fixed value. The value jumped around wildly when the engine was running.
After converting to the 3-wire alternator with Idiot Light, the value on the multimeter jumped around just as wildly again. When the engine is not running, the device shows 12.7 volts.
I tested the alternator with another battery on the workbench with the idiot light. Everything worked, the charging voltage of 14.4 volts could be read perfectly.
another thing comes to mind, I also had problems with the ignition flashing so that I could not determine the ignition timing.
Could it be that an electrical component is spitting into my electrical system?
Unfortunately I have no idea, I'm at a complete loss.

Thank you in advance, Best regards
Joe

[BRENT in 10-uh-C]

Originally Posted by henryford30

Hello Specialists


I bought my 30' Ford last year. At that time, the vehicle had already been converted to 12 volts.
Now I wanted to replace the 1 wire alternator with a 3 wire alternator.
I had the problem that the charging current could not be measured, the multimeter showed me some values, but no fixed value. The value jumped around wildly when the engine was running.
After converting to the 3-wire alternator with Idiot Light, the value on the multimeter jumped around just as wildly again. When the engine is not running, the device shows 12.7 volts.
I tested the alternator with another battery on the workbench with the idiot light. Everything worked, the charging voltage of 14.4 volts could be read perfectly.
another thing comes to mind, I also had problems with the ignition flashing so that I could not determine the ignition timing.
Could it be that an electrical component is spitting into my electrical system?
Unfortunately I have no idea, I'm at a complete loss.

Thank you in advance, Best regards
Joe

Joe, if the charging rate could not be determined, it was because there was not any load detected by the Ammeter, -or the wiring is routed incorrectly.

Next, is this "3-wire Alternator" using an external regulator? If so, you should have a Field, a Regulator wire, a Ground, and a wire to the lamp. Do you have these correctly routed?

I am not following you when you say the ignition was flashing. Can you elaborate??

[Bob C]

Use an analog meter, digital meters do not like the Model A ignition system.

[henryford30]

@ Brent
Hi, thanks for the quick reply.
When I bought the Ford, the ammeter already stopped working, I thought the ammeter was disconnected during the conversion to 12 volt. I haven't driven that much yet, I've repaired the other things first.
The alternator has an internal regulator, the alternator is also earthed.
I couldn't read the ignition timing with my digital ignition gun because the value was always jumping around.
Is there a wiring diagram for the wiring to 12 volts for the Model A? Something like that would help me a lot!
Can I also operate the original ammeter with the 12 volts or will it break?
Is it really possible that the ignition system does not allow measuring with digital measuring instruments? Like Bob C writes?

Thank you very much in advance

Joe

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[henryford30]

Hello Bob C
Thank you very much for your help.
Of course that could be the case, I'll see if a friend of mine has an analog meter.
I will report back.

Best regards

Joe

[Badpuppy]

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A DVM uses a sampling method, which is fine for reading steady DC. The problem with the A is that the ignition coil places voltage spikes on the battery line while the engine is running. A DVM would need a filter circuit to smooth the spikes, but an analog meter is the easier solution - its filter is built-in.

[rotorwrench]

Amp meters don't care what the voltage is, I would change to a 30-amp meter using an alternator but you really will only see what the battery is drawing to recharge. Once it is charged back to a normal charge state then the amp meter won't really read much of a load. It will tell you if the alternator is not working since it will show a discharge.

The model A was set up to run positive ground. Is your alternator set up for positive or negative ground? That makes a difference to the amp meter since it is polarity sensitive. I assume your alternator is a GM 10si unit. The two pin plug on them is strictly for the excitement of the field and the operation of the warning light. I would wonder how it is connected and what type of system switch is being used. The original switch (Electrolock) only controlled the ignition system and on the breaker side of the coil to boot. The screw terminal on the alternator is the one connected for charging the battery buss so it connects to the headlights, horn, and the terminal box on the firewall.

This link shows how it was originally wired.
https://www.mafca.com/downloads/Semi...ex%20Janke.pdf

Yours has been modified for a GEN warning light and you need to know how it should be wired up. We need to know system polarity and what type of ignition switch it has and how it is wired in orfer to help.

[henryford30]

A friendly hello to the specialists.
I have now got an analog measuring device and was able to measure the battery voltage perfectly. With the engine stopped I had 12.4 volts, with the engine running it was 14.2 volts. Even at higher engine speeds, the voltage didn't go any higher. So everything works as I wanted it to. The idiot light also goes out immediately after a short press on the accelerator pedal and the alternator then charges as it should.
@Rotorwrench
The system is switched to negative ground. I have installed the original ignition switch and an additional main power switch. So I am sure that no more current is flowing.
Thanks to everyone, this forum is just so great and helps so much with the experts on the forum !!!
Thanks again to all !!!

Joe

Translated with DeepL.com (free version)

[David in San Antonio]

Perhaps this is well known to others, but I’m wondering why someone would prefer one kind of alternator to another (1 wire or 3 wire)?

[rotorwrench]

The 10si is three wire set up. When modified, it will self excite just using one wire but the rpm has to come up a bit to excite the field. Using the other two wires as intended, it will excite immediately after start and the warning light turns off as it excites.