Good switched 12V source to excite alternator?

qwertyd10n · Post by **qwertyd10n** » October 24, 2011, 9:17 am

Good morning everyone,

I was cleaning up my underhood wiring last night and have everything taken care of except for the switched 12V source I need for the new 3G alternator I'm going to be installing. I bought a PA Performance 1614E alternator and decided against the one wire option.

I was thinking of coming off the back of the ignition switch and running it out the loom that runs down to the engine (the one that includes the temp sender, oil light, oil pressure gauge, tach, and coil wires). Is that the best place to find a 12V source?

As always, any thoughts or input are appreciated.

Cheers,
Dion

bobenhotep · Post by **bobenhotep** » October 24, 2011, 8:19 pm

normally it gets that from the generator light. if the alternator is anything like a delco, make sure it is connected to acc power and not ign.

qwertyd10n · Post by **qwertyd10n** » October 26, 2011, 9:10 am

Why would that be? Wouldn't the alternator only need that 12V source to excite it when the engine is running?

manimal · Post by **manimal** » October 26, 2011, 9:32 am

I have wired in Ford 3g and GM CS144 alternators using a '194' bulb to excite the alternator. I would go from an ignition HOT on one side of the bulb and the other side of the bulb would go to the excite wire on the alternator. This not only excites the alternator, but also acts as a warning indicator if the alt. should fail.

bobenhotep · Post by **bobenhotep** » October 26, 2011, 9:33 am

i know with a delco alternator if you hook the light up to ignition power and you have a relay running your ignition system, the power will flow back off of the alternator and self energize the circuit. in other words, you will turn your truck off and it will keep running

manimal · Post by **manimal** » October 26, 2011, 9:39 am

Yeah I didnt mean on the ignition side, I run from the power block or a power junction "KEY ON" source.

bobenhotep · Post by **bobenhotep** » October 26, 2011, 9:56 am

that is how i would do it also. with an indicator light. I usually run delco 63 amp alternators, because they are cheap and common.

qwertyd10n · Post by **qwertyd10n** » October 26, 2011, 6:51 pm

So let me see if I understand this right... If I extend the exciter wire off the alternator to one side of the existing ALT light in my dash and then run a wire from the other side of the light to a 12V source that is hot when the ignition key is in the "run" position, I'd get what I need?

Cheers,
Dion

manimal · Post by **manimal** » October 26, 2011, 7:21 pm

I have always used a "194" bulb. I was told it has the right resistance to excite the alt. Here is a diagram for you...good luck

Leeroy · Post by **Leeroy** » October 27, 2011, 6:07 am

I used the dash ALT light to excite mine, basically unhooked it off the old reg, plugged it into the green red on the new regulator and it hasn't missed a beat since. 14.4v at the battery when she's running.

Qwertyd10n, yes what you said is correct.
Only risk with this setup is if the dash bulb blows the alt won't excite, but every alt that needs to be excited has this problem. I have never seen a ALT/GEN light blow and you should realise if it does blow, becuase it wont be glowing just before you start the engine!

qwertyd10n · Post by **qwertyd10n** » October 27, 2011, 9:02 am

Hey Leeroy,

Thanks for the input... It makes me feel more confident about doing what I'm planning.

Couple of things... I'm thinking of running a 560 ohm resistor in parallel with the ALT light so if the bulb burns out the alternator will still excite (as per the diagram above).

As to just unplugging the old regulator wiring and plugging in the new green/red wire on the new one, I've removed all the old regulator wiring and the old external regulator. I was planning to just run an exciter wire into the cab from the new alternator. On my '66 Wiring Diagram Manual, the Charge Indicator or ALT light should have two wires running to it... A black-green and yellow-black... Do you have any idea which one might be hot when the ignition key is on?

Cheers,
Dion

Leeroy · Post by **Leeroy** » October 27, 2011, 4:57 pm

Resister is a good idea incase someone else is driving the slick and doesnt pickup the light is burnt out.

On mine, I use the yellow black as the exciter wire.
Seeing we have different model year slicks, I would check it just to be sure. Very easy to do with a test light, touching the yellow/black wire, have a helper put the key in the run position and make sure the test light illuminates and your good to use that wire.