Alternator warning light.

[H20rider]

Does anyone have a simple diagram of connecting a warning (led) light to a 1g ford alternator?
I have an in dash voltmeter, but want a more immediate alert.
I do not want a battery level indicator….but rather a light that goes on as soon as the alternator stops charging or charging sufficiently.

Or, instead of a diagram, which wire becomes grounded if the alternator is not functioning?

There are so many schematics that include resistors to excite the alternator and diodes to prevent current back flow, but these all seem to have different ohm values etc.

Or, is there a plug and play module? A company in Australia has one but they seem unresponsive….and pricey.

 

[jamesroney]

Take ignition power to an ungrounded (2 wire) incandescent light bulb. Run the other wire of the light bulb to the unused stator terminal on the 1G.

When the alternator is not charging, it will ground the light bulb, and the bulb will glow.
When the alternator is charging, it will put +12 on the light bulb, and the light bulb will go out.

That should do it. @DirtDonk can probably help more.

 

[Oldtimer]

Maybe?

The stator terminal output is max 7 volts AC.
Not sure incandesent bulb will go out with 12v dc on one side & 7v ac on other.

What say @DirtDonk ?

 

[DirtDonk]

Don’t ask me! I still use an ammeter!

Just kidding. I have different opinions on the subject.
Never thought about doing at the way James suggested, but it makes sense. Just as an indicator.
Would not have any effect on charging if the bulb went out, so you don’t need the bypass resistor

 

[H20rider]

Nice. Thank you all!

 

[jamesroney]

Nice. Thank you all!

I think it's going to be a problem. @Oldtimer is right, and the stator sees unrectified current that looks like AC. So that's bad. Also, it will push that current back thru the light bulb, and back on to the ignition terminal. If that happens, you won't be able to turn off the Bronco. And it will put AC on the ignition coil. And that's bad.

But you could use the stator winding signal as an input to a relay. That would isolate the AC, and as long as the alternator is charging, the relay would stay on. The bulb circuit is the same. One side at +12, and When the relay is pulled on, the bulb terminal goes to +12. When the relay drops out, it goes to 0V. (GND)

Sorry about that.

 

[DirtDonk]

The standard alternatives, would be to either wire it just as Ford originally intended when used with a lamp and utilizing all four positions of the regulator. Or, utilize the existing green with red stripe wire from the ignition switch to the regulator.
Adding just the bulb and bypass resistor yourself.

I’ve been dragging my feet for years, trying to make a little re-sellable kit to do just this. Ammeter or not, I always thought that having a lamp that gets your attention would be a good thing.
I thought I had something with Dakota Digital, but the parts turned out to be kind of odd and not intended for that purpose.

 

[DirtDonk]

With the latter method, using the Green w/red wire as it sits now, and maintaining the 3-wire connections at the regulator, you MUST use some kind of bypass resistor in case the bulb ever burns out.
Just like in any vehicle using a warning lamp, the light will come on when you turn the key to on, and then go out when the alternator is charging the battery.
So this is the test you use to make sure the bulb is still working. When the bulb burns out, it won't light up when you turn the key and you know you need to go and replace the bulb, or fix the circuit if it's a wiring issue.
If the bulb burns out and you don't have the bypass resistor, the circuit is broken and the regulator will never get the key's signal to let the alternator charge.
You might be driving along in the middle of nowhere when this happens, leaving you stranded with no charging system and no indication there was a problem because the lightbulb did not light up.

The resistor part, uses a resistor that is just slightly higher in resistance than the bulb itself. This way the bulb always is the first circuit and lights up when expected. Only going through the resistor when the bulb fails.
If the resistor did not have as high a rating as the bulb, then it literally becomes that famous "path of least resistance" and though the alternator will work, the light will never light up. Or will light up only dimly and at inconsistent times. Not much of a "warning lamp" in that case!
Adding a resistor of slightly higher value than the bulb lets the electricity go through it when the bulb fails, and so around the broken bulb, continuing to excite/turn on the regulator.
And letting you know it's time to replace the bulb, without stranding you at the worst possible time.

Paul

 

[H20rider]

If I use the “I” terminal on the VR, is the other connection to a keyed (ignition switch) 12v?
If that is so, and I want to use an LED, should I include an incandescent bulb to allow the “I” terminal current have something to switch off? The reason I ask is that since an LED is a diode, it might not be affected by the opposing charges from the ignition and the VR.

Otherwise, the use of a relay with the start or charge as a trigger to open the circuit sounds interesting. The strator terminal only supplies about 7 volts, though. Is that sufficient to trigger and open a relay?

 

[DirtDonk]

You could find the specifications on the relays to see what the minimum voltage is required to trigger it. Pretty sure that most of the manufacturers include that data.
But I’m not sure using a relay is the trick here either.

I really don’t know how the regulator will react to the fourth circuit being connected. Even though it was mentioned previously, I don’t know if applying 12 V where it’s not expected would affect the function of the regulator or not.
There’s very possibly a reason that Ford did it that way. My feeling is that if you use the I terminal, you should reorient the wiring to use the traditional orientation for a car with the light.
Even though I’ve thought about it for years, I’ve never actually tried it.

I think the previous mention of incandescent instead of LED is for just this reason you’re contemplating. Not sure how it would act as an indicator.
I’m sure they use LEDs nowadays, but they also have computers controlling the alternator and telling the lights what to do.
I’m not sure how to make an LED work because I don’t know all the details from an electronic theory.

Hopefully James or Viper or whoever can walk us down that path with some more details.

 

[jamesroney]

You could find the specifications on the relays to see what the minimum voltage is required to trigger it. Pretty sure that most of the manufacturers include that data.
But I’m not sure using a relay is the trick here either.

I really don’t know how the regulator will react to the fourth circuit being connected. Even though it was mentioned previously, I don’t know if applying 12 V where it’s not expected would affect the function of the regulator or not.
There’s very possibly a reason that Ford did it that way. My feeling is that if you use the I terminal, you should reorient the wiring to use the traditional orientation for a car with the light.
Even though I’ve thought about it for years, I’ve never actually tried it.

I think the previous mention of incandescent instead of LED is for just this reason you’re contemplating. Not sure how it would act as an indicator.
I’m sure they use LEDs nowadays, but they also have computers controlling the alternator and telling the lights what to do.
I’m not sure how to make an LED work because I don’t know all the details from an electronic theory.

Hopefully James or Viper or whoever can walk us down that path with some more details.

Don't wait for me. I'm lurking, but I'm too busy in the garage this week. Air Force Bronco is taking all of my time...sorry.

 

[DirtDonk]

No worries. Will wait for the full report.
Planning to put any special wording or serial numbers or ID markings on the door?

 

[jamesroney]

No worries. Will wait for the full report.
Planning to put any special wording or serial numbers or ID markings on the door?

I'm going to media blast and paint next week. Funny that you would mention doors. I have to make a Bonsai run to Lodi to pick up some hinge pins and rebuild my hinges for paint. I surewish you had the philips head hinge bolts in your catalog.

Looking for markings from the period. My dad was in SAC / MAC at Travis, but I'll probably stick with the McClellan ID. But definitely need help with the correct nomenclature. It's hard to find pics of Military Broncos from the 60's.

 

[H20rider]

Does the stator terminal only show a charge when the alternator is functioning (charging)? And if charging is not occurring does it cease to have a charge? Because….

Here is something I just tried. I connected an LED to the stator terminal and then to ground. The LED lights up when the engine is running, but goes off when the ignition is on but the engine is not running. Now, I realize that a light that just tells you if the engine is running would be useless. But, hopefully that is not why the light goes on. If the stator terminal only carries a charge when the alternator is functioning, then this set up could work as an “anti-warning” light. That is, glowing when all is well, but extinguished when a charging problem occurs.
It is not usual, granted. But a small, obvious, but non-distracting dash LED would probably be acceptable to me.
So:
1) Will it work as described?
2) could it cause any problems with the alternator?
Thanks

 

[73azbronco]

sorry, but your most immediate alert, is in fact the voltmeter, or even better the old school ameter on the dash showing negative.

 

[DirtDonk]

Yes, the stator terminal on the back of an alternator is only powered when the alternator is spinning.
I don’t know if the voltage varies based on RPM or output, but it definitely only works when the alternator is spinning.
But I don’t think previous descriptions had an indicator light working that way. But I’ll have to go back and reread some of the suggestions. See if anyone (especially me!) put it out that way.
(Edit: Yes, as James said in the first response, you use the stator as a ground.
The power to illuminate the light still comes from the ignition switch.)

I believe that if you were to use the stator terminal to indicate when the alternator is functioning, you would use it as a ground.
Power to the lamp from the key, through the lamp to the stator terminal.
When voltage output is present at the stator terminal, the light goes out. With no voltage, perhaps it allows the ground, and would function to allow the dashboard light to illuminate.
You can test that easy enough by seeing if, when the engine is not running, that the stator terminal shows to ground.
Continuity to the case of the alternator basically.

Get that ohm-meter fired up!

 

[DirtDonk]

Here again, I don’t know what the application of voltage to the stator terminal will do.
I don’t believe it will harm the alternator, but I don’t know that for a fact.
So the bottom line, from my standpoint, is still to use the Green with red wire for the lamp.

Until someone pops in that is, and says it’s perfectly fine to use the stator terminal.

 

[H20rider]

Here again, I don’t know what the application of voltage to the stator terminal will do.
I don’t believe it will harm the alternator, but I don’t know that for a fact.
So the bottom line, from my standpoint, is still to use the Green with red wire for the lamp.

Until someone pops in that is, and says it’s perfectly fine to use the stator terminal.

As always, thank you.

 

[Broncobowsher]

I don't have the factory wiring diagram from the '77 trucks anymore, it went with the truck when I sold it.
But I do remember that all 3 different wiring diagrams were in that single manual. The Bronco, the truck with ampmeter (different than Bronco ampmeter), and truck with indicator light. Shouldn't take much to study the 3 and make a simple wiring on how to do it.

 

[Steve83]

The easiest most-reliable way to accomplish this is to swap to a 3G; its VR is built with this function. This page shows how easy it is to wire it into an eB:

(click this text)


The S terminal of a 1G would be a weak ground when the alt is not working, and an ~18V AC power source when it is working, so I don't think there's a simple way to use it to trigger a light.

The only other way to really (directly) know if the alt. is charging would be to compare the alt. output voltage to the battery positive, which requires a shunt resistor (high-current low-resistance) between them and some voltage indicator across the shunt. That's exactly what common modern shunt ammeters do. When current is flowing through the shunt, there's a voltage difference across it, which the gauge measures.

https://www.amazon.com/dp/B013PKYILS/?tag=classicbroncos-20

An LED can also indicate voltage, but only in 1 direction, and you'd have to size the shunt to the LED to get the voltage indication you want (typical LED voltage is ~0.6~1VDC). Since it's so low, it may also work with an inductor, but that'll take more effort (either engineering or experimentation) to get it to work the way you want.

https://www.amazon.com/dp/B01M8LCWNW/?tag=classicbroncos-20