Warning light for 12 volt conversion

I am close to being done with a 12 volt conversion on my farmall c everyone has indicated there needs to be a warning light to excite the altenator..
The only kind of lights I kind find are LED lights is this enough to do the job or where can I buy a regular 12 volt socket and bulb that will work. Any
suggestions or comments appreciated

The socket linked to will work get the incandescent bulb to fit. The red connects to the ignition (before a ballast resistor if it has one) the black one to the #1 spade terminal. Jim
socket

I used to use a small red flat indicator light about the size of a dime. it took about a 3/8 hole and you just pushed it in and looked factory. when it started charging the light went out.

You can use a light bulb or diode or a ballast resister or even a switch. I have all of those and have done ones with an oil pressure switch so when oil pressure came up it excited the alternator. A light bulb like used for say the temp gauge or other such gauge for lighting works well

IMHO,a 'warning light' is a wives tale.I don't think it is necessary. I have done several 12 volt/one wire(delco) alternater comversions,havent used a light on any. All work as they should. Charge as soon as the engine starts. Have never had one have drain when stitting.Did the first 15 years ago(superM),the last one last month on my wifes SuperC.Am I missing something?

It's a very good idea to have a lamp, a diode, or a resistor in the circuit to the #1 "excite" terminal.

Any of the three will protect the alternator.

This has nothing to do with draining the battery once shut down, it has to do with current flowing OUT of the #1 terminal while the engine is running, or coasting to a stop.

The alternator's diode trio is designed to produce a few Amps to supply the rotating field with power as controlled by the voltage regulator, but under certain circumstances current can be drawn from the terminal which can damage the diode trio or circuits in the voltage regulator through which it passes.

A lamp or resistor limits this current to a safe level, and a diode prevents it from flowing, at all.

If it's connected directly to the ignition circuit, when the ignition switch is shut off, power will "backfeed" from the #1 terminal to the ignition system, keeping the ignition circuit powered even though the ignition switch has been shut off, so the engine won't "die".

Also, if there's ever a failed connection or even a loose/poor connection in the alternator to battery wiring, the previously mention components can be damaged, as the "excite" circuit will try to charge the battery even though the heavy wiring that's supposed to carry the charging current isn't doing it's job.

I use 1N5408 diodes, which are way more than adequate for the job, but cost only a few cents when bought in quantity.

If you have trouble sourcing just a single diode, I'd be happy to mail you one is you send me a stamped self-addressed envelope.

<img src = "https://www.gondtc.com/~blweltin/Bob/DelcoSIA1A.gif">

<img src = "https://www.gondtc.com/~blweltin/Bob/DelcoSIB1A.gif">

<img src = "https://www.gondtc.com/~blweltin/Bob/AlternatorHarness3.jpg">

A warning light IE a charge indicator "idiot light" in the excitation circuit is one of a few possible methods to initially excite an alternator plus prevent ignition feedback causing the engine to still run even with ignition off......? Other methods to allow for initial excitation and prevent run on with ignition off are a simple diode or just a simple 10 or so ohm resistor.

HOWEVER if you go with an idiot light charge indicator use a small INCANDESCENT BULB NOTTTTTTTTTT AN LED BULB

A diode or a resistor or an idiot light can (among other methods) wire in series between the ignition switches IGN output or the coils input to the small 1R terminal on side of alternator.

John T

Jim?s link didn?t work for me. Here is a link to another option. A 194 bulb and socket will work. You should be able to fashion a tin rain protector for this to mount on the dash or operators station. There may be other premade options available like license plate lights but the ones I?m thinking about use a 1 inch plus hole which may be hard to get it to look nice.
Socket

What if the tractor has a mag and there is no ign sw.?

Are you using one wire alternators? If so they do not require a connection to #1 pin.

Plumb an oil pressure switch into the oil pressure gauge line. It would have to be an off/on type switch that works in the pressure range of you tractor. That's what I did for one of mine that has a mag.

OTJ

A DPDT switch can ground the mag to stop the engine while on the second set of contacts provide excitement. Jim