Puzzled two

[daveymc29]

So, here's the Ace electrician with a question for the experts. In "puzzled" I explained that my alternator quit on me for unknown reasons. A friend came by and we looked it all over visually and he told me to pull the little rectangular cap off the top rear of the alt. He put a screw driver between the two poles just exposed a and then I started the car to find that the ammeter showed a normal rate of charge for having just cranked the engine and a couple of minutes later it had returned to a couple of amps on the plus side, indicating to me that the alt. was now functioning properly after the momentary connecting those two poles. He told me that he had to connect one of those poles to the output side of his alt. on a car back a few cars, but he didn't know why or which one had to have the jumper (extra wire) to get it to self excite. We stopped and restarted the engine a few times and it seemed to work. Later I started it up and drove around the block, it wouldn't go into the plus side again. Any clues? What do those two poles do and if one needs to be connected to the feed line, which one is it? How do I tell one from the other?

[J Franklin]

Kind of like a bad cutout.

[Corley]

On a 3 wire alternator, one of those is for sensing the output voltage, and one of them is for exciting the thing to get it to start charging. On a one wire alternator, those should not be used, but may be hooked to some internal ckts for testing. It is impossible to say what function they may perform on the one wire alternator without knowing the internals of the regulator, and how they are connected, since by design, they should not need to be used. It seems your internal regulator has bit the dust.

One wire internal regulators are available on FeaBay for less than $8 for some models of alternators. In point of fact, one of those is all it takes to convert a normal 3 wire alternator to a one wire unit.

[Badpuppy]

https://alternatorparts.com/understa...ternators.html
explains a lot.
For external triggering you need a switched battery to the regulator #1 terminal through an (optional) incandescent idiot light.

I'd guess you've lost a diode from the "trio" which i believe is part of the regulator. Those guys sell them.

edit: nope, the trio is a separate part - 10 bucks.

good info at the bottom of this page too -
https://alternatorparts.com/10si-alt...-and-kits.html

[Corley]

Originally Posted by Badpuppy

I'd guess you've lost a diode from the "trio" which i believe is part of the regulator. Those guys sell them.

edit: nope, the trio is a separate part - 10 bucks.

good info at the bottom of this page too -
https://alternatorparts.com/10si-alt...-and-kits.html

No, not the diodes, when a diode fails, the output contains more ripples, but his problem is failure to start charging. Most likely an internal regulator issue.

[daveymc29]

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Okay, so here's what I did. I had a fuse in the system in a fuse holder that screws to the starter. Once before on another car I had found the holder to be defective. I took that holder out of the system and behold, everything is back to normal, alternator is self exciting without having to rev the engine when starting. Ammeter shows charge in a bit over 5 lines until I have driven around a couple of blocks and by then has settled in at about one line on the plus side. I still don't know a lot about alternators but the bottom of the fuse holder showed signs of having been quit hot though I couldn't see any arching onto the started. It never did trip the 30 amp circuit breaker but my guess is that the contact between battery and alternator would become lost and not return on its own. While touching all those parts, removing and reinstalling the breaker and such it probably restore the connection long enough for me to drive a couple of minuted and maybe the extra load of the brake lights caused it to heat and lose the continuity again. Anyway, now I have an inline fuse in the ignition circuit and will put another into the light circuit.

Thanks for helping me to understand the alternator better. I will drive the car several miles tomorrow and report back. I do believe the initial problem was the fuse holder so I will get a better holder and probably run a 30 amp circuit breaker as was in the errant fuse holder

Thanks to all. I see it isn't rocket science to keep these little gems running. See you all at Sparks end of the month. Drop by the repair area and say "howdy."

[Badpuppy]

So, bad battery connection through the fuse - enough current for ignition but not enough power left to excite the alternator. That's a noggin thumper. One for the books, I think.

Chuck "Chunk" Thunk finds wife Huda in the trunk.

Huda Thunk!

[Jim/GA]

This is another example of why I recommend to everyone that they remove that exposed "mounts to the side of the starter switch" fuse holder and replace it with a fuse in a weatherproof holder that is fully soldered into the solid yellow wire that runs from starter to terminal box.

The exposed fuse holder has caused problems on more than one of our tours. And they often don't totally fail, just intermittently, so it is really hard to diagnose.

[Corley]

Many times with various electrical connections, I've found things that look tight, couldn't possibly be a problem, but even though it looks good, there is no continuity. Your VOM (volt ohm meter) is your friend, use it. Don't just check voltage sitting there, try it when under load and failing. Those fuse blocks are bad news.

[BILL WILLIAMSON]

Jim,
I used a 30 Amp, G.M. bayonet type circuit breaker, with a supplied Pig Tail lead, on the Yellow lead at the starter. Used 2, 20 Amp ones, individually, for the Horn & Lights----That's ALL you need, for excellent protection.
Bill W.

[daveymc29]

Problem solved. Replaced the ammeter. Took alternator back to the rebuilder and it test to 30 amp and 7.5 volts output. He suggested the ammeter and was correct.