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Super C - Idiot light:)

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banjoman09

Well-known Member
SO I have a new 12v alternator...new battery...and installed an "Idiot light" and wired it correctly .... tell me why please I
have to have it "full throttle" to make the idiot light go out and the alternator starts charging...? Thanks!
 
Because the tractor engine rpm and pulley set up is not like on a vehicle. Once it’s charging you will be fine.
 
If you can wire it like this diagram you won't need to rev it to make it charge.
cvphoto65380.jpg
 
(quoted from post at 10:36:20 12/02/20) what number bulb/lamp do you have in the light? Is it an LED light?
Click to expand...

GOOD point, rvirgil!

It needs to be a #194 lamp or one with a similar current draw.

A little incandescent lamp that draws significantly less current or an LED will cause the problem the O.P. is having.
 
I never have that problem if I use a diode instead of a light. The ammeter immediately moves to the charge side.

I'm pretty sure that the reason is because of the voltage drop across the bulb (12V) vs. the voltage drop across the diode (<1V). There's no voltage left to excite the alternator with the light configuration.
 
(quoted from post at 12:23:51 12/02/20) it came on it?
Click to expand...

When I upgraded my VAI to 12 volt I tried to use the pulley that came on the alternator bought on this site, but had to toss it away and get a smaller one.
 
(quoted from post at 11:03:25 12/02/20) I never have that problem if I use a diode instead of a light. The ammeter immediately moves to the charge side.

I'm pretty sure that the reason is because of the voltage drop across the bulb (12V) vs. the voltage drop across the diode (<1V). There's no voltage left to excite the alternator with the light configuration.
Click to expand...

It's all about the CURRENT.

If the lamp used draws enough CURRENT the alternator will quickly excite.

Some OEM applications using an indicator lamp placed a resistor across the lamp to ensure that the alternator would excite even if the lamp burned out.
 
Ok I have an incondescent light I bought at parts store- as I was instructed when I wired this in. Thats what everyone suggested.... I think I was told that LED would not have enough resistance. I have to remove battery and battery box to get into the wiring for the light; would it be easier to change pulleys? Thanks.
 
Pulley size should not matter with a 3 wire Delco alternator if it has a proper lamp, diode or resistor.
 
Have the same issue with JD50 with 3 wire alternator. Used idiot light that is supposed to be for this use from O’Reily’s. Kinda just learned to live with it. But perhaps someone here, who understands this stuff better than I, will suggest a resolution. Thanks.
 

"Used idiot light that is supposed to be for this use from O Reily s."

Was that light actually "cataloged" for use as a 10SI Delco warning light, or is that just some B.S. the counterman told you?

You wrote "But perhaps someone here, who understands this stuff better than I, will suggest a resolution."

I already did.

Use a #194 lamp or a lamp that draws equivalent current, OR parallel a resistor across the lamp.

The value of the resistor will be in the 10 Ohms to 50 Ohms range, depending upon the indicator lamp you are using.

If the value of the resistor is to low the light won't light or light very dimly, if the value of the resistor is too great it won't help the problem you are having.

A 10 Watt resistor should be fine.
 
I like the "Idiot light" because Im an "Idiot" ! The light stays on and will not charge until it goes out! At full throttle. So my last post on this I was given several answers that said to "install a incandescent" light and it will work fine! Now you say not? So heres the deal- I light from O'reillys did not fit the hole so I had to enlarge the hole - now it is "super-glued " in- so they only had one choice!
 
So can you just send me a pic or number of an "idiot light" that is round to fit my tractor dash...-red light- that is 10-20 amps
draw and I will buy it and install it- thanks!
 

Use a voltmeter across the battery terminals to confirm charging starts when the light goes out. Use a jumper wire and give the #1 terminal a shot of 12 volts and see if it starts charging at a lower rpm. If there is no change it would sound to me like your indicator light is working properly (and you said it was incandescent so it may be a 194 bulb or similar, check it and see). Then my thought is you need a smaller alternator pulley, tractors often need a smaller diameter pulley than cars and trucks as the engines turn slower. If it charges at a lower rpm with the jumper wire, add the resistor.

Do you have a working ammeter on your tractor? If so you could use an oil pressure switch to feed 12 volts to the #1 terminal and do away with the indicator light altogether.
 
A light bulb like the one that goes in a gauge to light it will work but the biggest problem with the light bulb is if it burns out then you have no charge where as a diode or resister is very unlikely to go bad
 
yes theres an amp meter and I want to keep it; It shows 15 amps when the light goes it..it charges. I really dont want to change
the new lamp out -I just put it in; it takes a major deal to get to it; can I buy an extra resister and hook it up in the wire
going to the light...which is easy to get to? Or just try to find a smaller pulley? Thannks.
 
(quoted from post at 12:42:54 12/02/20)
(quoted from post at 11:03:25 12/02/20) I never have that problem if I use a diode instead of a light. The ammeter immediately moves to the charge side.

I'm pretty sure that the reason is because of the voltage drop across the bulb (12V) vs. the voltage drop across the diode (<1V). There's no voltage left to excite the alternator with the light configuration.
Click to expand...

It's all about the CURRENT.

If the lamp used draws enough CURRENT the alternator will quickly excite.

Some OEM applications using an indicator lamp placed a resistor across the lamp to ensure that the alternator would excite even if the lamp burned out.
Click to expand...

Yes but if you put a resistor in parallel there, now you need a diode as well because you've essentially hard-wired it. It will backfeed the ignition switch and the coil, so the tractor won't shut off.
 
(quoted from post at 14:41:51 12/03/20) yes theres an amp meter and I want to keep it; It shows 15 amps when the light goes it..it charges. I really dont want to change
the new lamp out -I just put it in; it takes a major deal to get to it; can I buy an extra resister and hook it up in the wire
going to the light...which is easy to get to? Or just try to find a smaller pulley? Thannks.
Click to expand...

I would try a smaller diameter pulley and see what that does. What is the OD of the pulley you have on it now? Is it the right width to match the water pump/fan and crank pulleys? If it is too narrow and the belt is riding high that increases diameter and slows the rpm as well. Using a jumper wire as a test as I mentioned will tell you if you need to add a resistor. Can you find out what number the bulb is in the lamp? Ask the guy that sold it to you if you can't readily remove and check the bulb.
 
It takes much less current to jump start the alternator than it does to power the coil and distributor. Bulb and resistor limit the current to a level high enough to start the alternator, but not enough to back feed and power the coil.

A diode passes current one direction, blocks current the opposite direction. Properly wired will pass current to the alternator but block it from getting back to coil.
 
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