Alternator wire

[bob8619]

In this pic you'll notice that the wire I'm holding is disconnected from that clip going into the alternator. I've got 14.50 volts at the battery when running so its charging properly, so what is that wire for?

I traced the wire and it goes into the harness for the voltage regulator but it doesn't actually connect to the regulator, I'm guessing that this alternator is internally regulated so previous owner bypassed the regulator?

[sick472]

See if it goes to an Ammeter. That's my bet.

[bob8619]

Originally Posted by sick472

See if it goes to an Ammeter. That's my bet.

Ah yes I bet you are right

[Mr_Rich]

I don't have a schematic handy but that may be full-fielding your alt. That means it's not being regulated and you could cook your battery. It might cause possible acid damage in the battery tray area. 14,5VDC is too much. That wire looks like it's in pretty brittle and not good shape. Good news is that those terminals are pretty common in auto parts and the terminals and plug are easy to replace.

[bob8619]

Originally Posted by Mr_Rich

I don't have a schematic handy but that may be full-fielding your alt. That means it's not being regulated and you could cook your battery. It might cause possible acid damage in the battery tray area. 14,5VDC is too much. That wire looks like it's in pretty brittle and not good shape. Good news is that those terminals are pretty common in auto parts and the terminals and plug are easy to replace.

I mistyped it's actually 14.20 volts, is that still too much? The reason I even started messing with this is in search of what keeps draining my battery after sitting for a couple days, so maybe I did fry it and thats why its dying.

[bob8619]

I have to rev the engine to get the alternator to charge does that mean this is one of the single wire alternators? And if so, does that change anything in terms of that wire?

[ray_mcavoy]

Originally Posted by bob8619

I traced the wire and it goes into the harness for the voltage regulator but it doesn't actually connect to the regulator, I'm guessing that this alternator is internally regulated so previous owner bypassed the regulator?

Yes, from the pic you posted it appears that your truck has been converted to an internally regulated alternator.

The disconnected wire is for the "GEN" light (if your truck has the standard warning light cluster). That circuit also serves to "excite" the alternator ... in other words, cause the regulator to "switch on" when the ignition is on. Many regulators will "self excite", without that wire connected if the engine is revved up a bit, which sounds like what you're experiencing.

In addition to re-connecting that wire to the alternator, you'll probably have to install a jumper at the former external voltage regulator plug to complete the circuit. Try searching this site for external to internally regulated alternator wiring and it should turn up some posts by VetteVet with diagrams.

[bob8619]

Originally Posted by ray_mcavoy

Yes, from the pic you posted it appears that your truck has been converted to an internally regulated alternator.

The disconnected wire is for the "GEN" light (if your truck has the standard warning light cluster). That circuit also serves to "excite" the alternator ... in other words, cause the regulator to "switch on" when the ignition is on. Many regulators will "self excite", without that wire connected if the engine is revved up a bit, which sounds like what you're experiencing.

In addition to re-connecting that wire to the alternator, you'll probably have to install a jumper at the former external voltage regulator plug to complete the circuit. Try searching this site for external to internally regulated alternator wiring and it should turn up some posts by VetteVet with diagrams.

I reconnected it and did the jumper and now my alternator is self exciting which I'm pretty happy about. I don't think I have a generator light on my dash, at least it doesn't say GENERATOR on it like the ones I've seen. Is that same wire supposed to power the amp gauge on the dash though?

[ray_mcavoy]

Originally Posted by bob8619

I reconnected it and did the jumper and now my alternator is self exciting which I'm pretty happy about. I don't think I have a generator light on my dash, at least it doesn't say GENERATOR on it like the ones I've seen. Is that same wire supposed to power the amp gauge on the dash though?

The "generator" light is only found in the warning light clusters. The factory gauge clusters don't have that light since they have the "battery" gauge instead. And no, that wire is not connected to the ammeter/battery gauge circuit. That gauge has separate wiring that originally connected to the charging system through a couple of 4 amp inline fuses (one located near the external voltage regulator location and the other near the junction block on the fender by the battery).

[Andy4639]

This should help you.


http://67-72chevytrucks.com/vboard/s...185856&page=16

[davepl]

Originally Posted by Andy4639

This should help you.


http://67-72chevytrucks.com/vboard/s...185856&page=16

Except he's now running an internally regulated alternator so it's quite different than the original schematic, ESPECIALLY where the alternator is concerned. But does show the factory setup nicely!

[RichardJ]

Here is a simplified version of the charging circuit and it's from GM.

Notice that the resistance wire and the generator light, both terminate at the ignition switch and at the bulkhead connector.
This resistance wire is in the dash harness wiring. This resistance wire is in the harness, whether it has the Gen light or no light. As mentioned by someone above, a Generator Gauge is in a different circuit.
This resistance wire is the same in the '60s truck with external regulated alternator and in the '70s truck with internal reg alternator.

The voltmeter shown in the drawing was there for testing purposes.

[michael bustamante]

that red wire going from the plug to the post in back of the alt could be draining your battery. it was on mine. I had to run the red wire in the plug to the post on the fender where the battery hooks up

[Andy4639]

Originally Posted by davepl

Except he's now running an internally regulated alternator so it's quite different than the original schematic, ESPECIALLY where the alternator is concerned. But does show the factory setup nicely!

That has nothing to do with where the wiring goes. You don't change out the wires to the truck just to install a newer alternator. You either jumper the external regulator out are run the wires from the regulator to the alternator. Nothing else changes so the wires run to the same places.