The Stovebolt Site Forums The Shop Area The Electrical Bay LED warning lamp for Alternator?

I have a Delco 10SI Alternator fitted in my truck. I would like to use a 12v LED as the warning light on the dashboard, has anyone tried this, and did it work, or will I have to use a conventional lamp to connect to the F terminal on the Alternator?

Thanks, Stuart.

Gudday Stewie !
One simple answer for you.......yep it'll work just fine.
My burn-out car runs exactly the same set-up. http://i294.photobucket.com/albums/mm104/36chevy/burn3.jpg
We found a charging problem one weekend at a burnout competition and managed to overcome it by removing one of the tail light globes' and wiring it to the alternator f terminal as a resistor to the charging circuit.

After returning home and fitting a more modern LED light in the dash wired through the f terminal....it works a treat.

Hit the ignition switch...it comes on, hit the starter...it stays on, give it a rev and the LED goes out indicating the start of the charge cycle......try it mate, works a treat !

All the best, Doc Bob. http://i294.photobucket.com/albums/mm104/36chevy/burn1.jpg

Stuart,

Interesting. Does your 10SI have a 'F' embossed on the case adjacent to the DA plug? Does it have the number 1 near or below the 'F'?

Stuart

Stuart, there isn't an "F" embossed on the case as you describe, but there is a "1" embossed on the case behind the "F" terminal and a "2" behind the sensing connector. In fact, for my own information, I stamped these into the case before refitting it to the motor.

Stuart.

Stuart, Doc, and Stuart - maybe Alan,
I have an idot light wired in series in the #1 wire fron the Alt to the on/off switch of the key'ed ignition. Correct me if I am wrong here, but if the bulb burns out the truck won't start... therfore I need to make an aditional connection of something(?), in parallel. Can this be the # 1 wire itself, does it need a resistor of specific ohm, etc.? Unforturnately the carbs are on order so the vehical is not running, otherwise I would test the above theory instead of post. When I turn the key, the light comes on as it should, but should go off after the alternator starts charging? pull the bulb, turn key on, no voltage on the other side so this is my assumption.
Thought and ideas as always appreciated,
Brett

The bulb has nothing to do with starting. When you turn on the key, the bulb gets power from the switch and ground from the alternator so it lights up. When the alternator kicks in, it gets power from both directions and no ground so it doesn't light.

Brett,

Did you mean if the bulb burns out the alternator won't START to charge. I think this is accurate, but as Cletis said, it shouldn't have any bearing on the engine starting.

Stuart

The truck will start if the bulb burns out but the charging system won't work & the bat will soon go dead. You could make any hot connection to the term to get going but it will feed back & the engine will not shut off.

Thanks for the replies so far. My truck only had the Battery connection and sensing wire connected when I got it, and charged the battery OK without the field connection being connected to anything.

I was going to connect the warning lamp/LED to the the Field terminal that wasn't connected before. I'm just not sure whether an LED will work OK with the control unit in a 10SI alternator because of the tiny amount of current that would be flowing in the field circuit, so wondered if anyone had tried using an LED before with this particular alternator/control unit setup.

Understand the the 10SI connections look like this.
http://i103.piczo.com/view/3/h/b/5/2/u/p/w/0/w/z/t/img/i287317235_31052_5.jpg

Stuart.

Stuart,

To my knowledge, the alternator wouldn't charge unless the #1 terminal was supplied with a initial charge. This is true unless the regulator has been changed to one suitable for single wire operation.

There is a regulator suitable for single wire service that looks identical to the three wire version. It will allow the alternator to charge with only the BATT wire connected, with the sensing wire connected or with all three wires connected.

If this is accurate, I will surmise this is what you have. As far as the diode goes, there is a after market dongle for the DA plug that is used when there is no idiot light in the circuit.

This plug has a small diode installed in series with the #1 terminal and the vehicle power source. It's function is prevent engine run-on when the excitation voltage is pulled from somewhere not switched from the ignition system

Not being a electronics type, I would guess that if this small diode would work, then a small diode in a light emitting configuration would work too. I could be all wet on this though.

Stuart

Cletis,
So it is a balance of power. The key is turned on and the light recieves 12 volts of current. Simultaneously, there is zero curent being recieved from the alt on the alt side of the bulb. Thus the current is allowed to flow through bulb, lighting it, and kicking in the alternator regualtor in charging mode. When the alt side voltage of the bulb is equal to the switch side of the bulb, no current will flow, therefore the light goes out (technically I guess it gradually dims until it goes off completely). Cool!
Stuart,
Unfortunatley, I was not that far ahead in the thinking and Cletis squared me away on the first part; you do adress my second thought though, what do I need to do to insure the alt kicks into charging mode if the bulb does not funtion or come up missing? Let's say, a girlfreind steals it? How do I prevent myself from driving home from the strip joint, noticing the headlights are gradually getting dimmer, wind up stranded on the side of the road, and having to call her for a jump? Wire a resistor or something in parallel conducive the needs of the voltage regulator or straight wire?
Brett

Brett,

I don't have a definite answer for you. The 'GEN' light or charge light doesn't see a lot of run time, so it would probably last for a million years. Add to this the fact that turning the key to ON will illuminate the lamp and prove that it works before the rig is started.

Stuart

true andsince I have te original Ampmeter as well should not get stranded. I will see if I can get hold of M.A.D. ann see what his thoughts are. I wired my truck via him, Hovarth, and EZ wire.
Will let yall know what he recomends.
Brett

Cavebull, I'm not sure that your question doesn't tell me you know more about the alternator than some that tried to answer your question.
Put a 10 ohm, 10 watt resistor in parallel with the light. That is how GM did it and they did it for the very same reason you ask. Most Chevy's have a resistance wire inside the harness, under the dash. This drawing shows the resistor connected to the ACC connection, but don't worry about that. just put the resistor across the light socket.
If you are using the older alt with external regulator, it's still the same.

Indicator light

Richard,
Where do I go about getting a 10/10 resitor? Assume a local auto parts so what can I reference Chevy wise at the local Auto Parts?
Brett

Radio Shack

thanks Cletis and all.
Brett

Interesting information about the parallel resistor for the bulb in the field circuit being a standard fitment on some trucks. What I think I'll try is a 24 Ohm resistor in parallel with a 12V LED in the dash, this should mimic the resistive loading of a 2W bulb (with a stone cold filament) in the circuit, hopefully the current split through the parallel resistor and LED will be sufficient to light up the LED.

Thanks to all. Stuart.