Guys I've got a newby question for the experts here.

Thread Starter

xhdskip

Joined Dec 16, 2015
12
Guys I've got a newby question for the experts here.
I've got a problem, why else would I need help right?
I'm wanting to put a 12V dc resistor in line on my alternator.
Which way does it need to go, or does it even matter?
I've watched several you tube videos and can't seem to find the answer.
This is a 470 ohm 1/2 watt resistor with 5 colored bands,
red blue black and what appears on the blue resistor as a yellow band.
One end appears bigger than the other, ANY help would be appreciated.
 

dl324

Joined Mar 30, 2015
17,012
I'm wanting to put a 12V dc resistor in line on my alternator.
Which way does it need to go, or does it even matter?
I've watched several you tube videos and can't seem to find the answer.
This is a 470 ohm 1/2 watt resistor with 5 colored bands,
Why would you ever want to do that?

There are no 12VDC resistors. Most are rated for at least a couple hundred volts.

The output voltage of the alternator will depend on RPMs.

You have the bands backwards.
resistor_color_codes_chart.jpg
 

MrChips

Joined Oct 2, 2009
30,984
Besides being a strange request (there is no such thing as a 12VDC resistor), your thread title is totally useless.

"Guys I've got a newby question for the experts here."

Put a title that gives readers some information pertaining to the problem. Something such as this would be better:

"What resistor should I use in line with my alternator?"
 

Thread Starter

xhdskip

Joined Dec 16, 2015
12
I had no idea there is no such thing as a 12 Volt resistor,
the resistors the guys in the you tube videos are using are all on vehicles,
so I assumed they were 12 Volt.
What I'm trying to do is get resistance on the "L" wire so the alternator "comes on" and starts producing power.
 

Dodgydave

Joined Jun 22, 2012
11,320
I had no idea there is no such thing as a 12 Volt resistor,
the resistors the guys in the you tube videos are using are all on vehicles,
so I assumed they were 12 Volt.
What I'm trying to do is get resistance on the "L" wire so the alternator "comes on" and starts producing power.
Why don't you give us the alternator model, then we can find out how it needs to be used to give out the voltage.
 

dl324

Joined Mar 30, 2015
17,012
the resistors the guys in the you tube videos are using are all on vehicles
There are a lot of people on YouTube that don't know what they're talking about.
What I'm trying to do is get resistance on the "L" wire so the alternator "comes on" and starts producing power.
You should have said that in the original post. Since there are many types of alternators, the type of vehicle it's in or the part number would be helpful.
 

MrSoftware

Joined Oct 29, 2013
2,208
I had no idea there is no such thing as a 12 Volt resistor,
the resistors the guys in the you tube videos are using are all on vehicles,
so I assumed they were 12 Volt.
What I'm trying to do is get resistance on the "L" wire so the alternator "comes on" and starts producing power.
Forgive these guys for being a little rough on someone trying to learn. ;) Can you give us more back story on what you're trying to do? Are you trying to adapt an alternator to a car that it wasn't originally designed for? As mentioned above, if you can post any information about the exact alternator you're dealing with, and what you're trying to do with it, then we can give more useful information.
 

MisterBill2

Joined Jan 23, 2018
19,042
INDEED!!
First we need to know what the goal is, the the details as to what the alternator is, and if it is on an engine so that it can be driven, and if it is already connected to a battery.
 

Thread Starter

xhdskip

Joined Dec 16, 2015
12
First off, Thank you to everyone that responded.
Here's what I've got and what I'm trying to do with it.
It's a CS alternator AD model, fits GM vehicles 99 to about 15?
4 pin , 1, S pin, 2 is the L pin ,#3 is the F pin and #4 is the P pin for the pulse.
I'm trying to get it to put out a charge. Naturally it has a #6 gauge going from the back of the alternator to the battery.
The input is where I'm thinkin my problem is, because I have it wired from the battery to a 3 pin ignition switch
that the pins are marked as Bat (for battery) then another pin says SOL which I assume is for the solinoid on the starter,
and lastly the third pin says ACC which again I assume is accessory. Which the "L" wire (idiot light) and charge out of it.
the "F" (field) wire is wired to the ACC pin. It spins up like it's suppose to but I'm NOT getting any charge out of it.
I was thinkin IF I put a resistor in line to the light, MAYBE it'd make it come on.
I'm lost if ya can't tell, and ANY help would be appreciated at this point. Thanks again gentlemen
 

MisterBill2

Joined Jan 23, 2018
19,042
"ACC" is the standard abbreviation for accessory, which is on after the engine is running. So that could be the pin that starts it operating to put out current. Consider that you would not want it to stop charging just because the idiot light burned out, would you?? If you have a voltmeter (multimeter) you can check to see which pin gets powered when the engine is running, if the rest of the wiring is present.
 

geekoftheweek

Joined Oct 6, 2013
1,249
What exactly are you doing with it? Alternators generally need to be spinning at a minimum RPM before they will start to produce power. If you are retrofitting it onto another engine then that part should be covered...

I found this article which may shed a little light on the issue. https://www.chevyhardcore.com/tech-...-wiring-tips-for-popular-gm-charging-systems/

The article states that directly connecting power to the L terminal without resistance will burn out the regulator. If you have already done this it may be the cause of the problem.
I am going to assume since there is a connection to the ignition on the F terminal that it will not make a difference if there is a connection to the L terminal, but I could be wrong. Are you sure your connection to the F terminal is getting power?

Assuming you are mimicking a 2 watt bulb at 14V you will need a 100 ohm resistor rated for at least 2 Watt. I would go at least 5 Watt myself, and you'll probably find 10 Watt about the same price... https://www.amazon.com/Qjaiune-Prec...7YzTX2lABTtzP_ZpiR-AUa9bZHxoC34AQAvD_BwE&th=1 You can find individual ones on DigiKey, Mouser, etc. for less, but in the long run with shipping costs it will probably end up being more.
 

Thread Starter

xhdskip

Joined Dec 16, 2015
12
Both the "F" wire and "L" wire are wired to the ACC pin on back of the switch.
They are both getting 12V when I turn the switch on.
The light comes on when I turn the switch, and is suppose to go off when The alternator starts producing power,
at least according to this video
it's a youtube video.
 

geekoftheweek

Joined Oct 6, 2013
1,249
Both the "F" wire and "L" wire are wired to the ACC pin on back of the switch.
They are both getting 12V when I turn the switch on.
The light comes on when I turn the switch, and is suppose to go off when The alternator starts producing power,
at least according to this video
it's a youtube video.
Without seeing the setup and being able to poke around myself the only explanation I can think of is either the alternator is not turning fast enough, or there is a break in the "F" part of the circuit somewhere. Can you back probe your connection at the alternator with everything connected? Stick a paperclip or stiff wire between the wire and the seal on the back side of the connector with everything connected and measure the voltage.
 

MisterBill2

Joined Jan 23, 2018
19,042
While a brush-type DC generator does start to produce a voltage at a lower speed than a diode rectified alternator, the voltage is proportional to RPM, and so the available power only increases in a fairly linear manner as the speed increases. And the older generators also required power for the field coils. The big deal was the current limitation of the brushes, as well as the need for replacements more often.
 
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