generator wiring question

[tom61]

Hi All:

I have an old Pearson Triton, relatively new to me, and the wiring is more interesting than I'd expected. Trying to determine why the ammeter was always reading zero, I discovered that it was wired to the starter solenoid, apparently measuring the current to the solenoid so you can see it twitch when I press the starter button. Not sure why that was interesting to someone...

Anyway, in setting out to rewire it, I ran aground on these questions, wonder if anyone can help me:

1. How can I tell the difference between an ammeter that needs a shunt and one that is meant to read direct? I am guessing I have the latter, but pretty sure I can't safely infer anything from its installation, despite how neatly the wires were crimped and wrapped.

2. The engine has a generator and external voltage regulator mounted on the wall of the engine compartment, with a 12v bus next to it. Can I rewire the ammeter within the engine compartment (without having to lead a wire up to the ignition switch) so that it will not create a battery drain when the engine is off?

3. Is there a schematic somewhere of an A4 with a generator? I found a reference to such a thing in an old forum post, but the link was dead. A decent description of the voltage regulator operation would be helpful, too. "ARM"? "FLD"?

4. What *should* the generator terminal voltages be when all is well? I get +14v on one terminal, which seems healthy to me, but what do I know? The other terminal might be 6v and it might be a varying voltage that my primitive tester can't grok. Or it might just be enough paint and crud on the terminal that I wasn't getting a good reading.

Thanks all!

[joe_db]

There are a LOT of threads on these subjects. To start with, do you actually mean a literal DC generator with brushes and all from decades ago?
We can help, but I think some photos and whatever you can sketch out as a wiring diagram would help a ton.

[tom61]

Ok, will go take some pictures. And yes, I think I mean an old generator, with three terminals and an external voltage regulator. The boat is from 1960, and it appears to me that the engine has not had much done to it since it was a mere chip off the block. It runs as is, and I'm hoping to improve it a little bit (installed a proper through hull and engine flushing tee last month) but want to make my early investments in time on other things on this boat.

I have no doubt there have been lots of conversation on these topics over the years, but my searching skills seem inadequate since I have not been able to find them to answer these questions. And some threads I did find are old enough that the promised links to wiring diagrams are dead.

[ndutton]

This diagram should help

[joe_db]

I would seriously consider getting an alternator.

[tac]

As to your ammeter, see,

http://www.moyermarineforum.com/foru...8&postcount=24

In general, if your ammeter is the standard automotive round 2-1/16” ammeter, then it probably has an internal shunt, and is wired in series with the load using biggish wires, like #2, #4, #6, #8. These meters usually are zero center scale, so they can read positive or negative, and look like the below image.

If the meter has an external shunt, the two wires should be small, like #14 or #16, or even smaller, since the shunt output to the meter is only a few milliamps at a few millivolts. And you can follow these two small gauge wires from the meter back to the shunt, which will have two large wires from the load. In addition, it is customary (even in the ‘60s) to mark meters that use shunts, either on the back or on the face, with the shunt ratio (“100A = 50mV”).

[tac]

As to ARM and FLD, they are abbreviations for the generator’s armature and field connections. Here is a drawing from an old Atomic 4 manual, Figure 22. It looks like it’s from the same document as Neil’s drawing, Figure 21-A. There also are Triton and Alberg sites galore. Some of them may have more info on your equipment.

[Al Schober]

Concur with the assessment of the ammeter. Good sized studs is a sign of a direct connect ammeter. Problem with these being excess wire length to go from the current source to the meter then back to the battery. The way to go these days is with a battery monitor that does voltage, current, and state of charge.
Re: the generator. Worst part is the mechanical voltage regulator - major source of problems. I had one boat with alternators controlled by mechanical regulators - problems with the regulators. Recommend you convert to an alternator with a 3 stage electronic regulator. I think my last one was a Balmar ARS-4 - not state of the art, but quite satisfactory. Nice to watch the LEDs come on as the controller progresses from current limited to voltage limited then finally to float.
Also recommend separate batteries for house and starting. Each battery with its own ON/OFF switch. For starting, a Group 24 is fine. For house, whatever you need. Keep the individual batteries movable - I found Group 31s too heavy for me and went to Group 27s. I ended up running my alternator output directly to the house bank. When it came up to voltage, a VSR would send current to charge the start battery.
This will probably require some rewiring. As you do this, keep an eye on your voltage drops in the cables. I found that I had to add an extra ground cable to the house bank to cut down voltage drop. House bank was close to the distribution panel, but about 10' away from the engine/alternator.