So do I have a Three wire or two wire alternator?

[ol Curt]

I started the truck up to pull it outside today. I had a generator light on and it stayed on while running. I checked my voltage at the battery while it was running and it was only 11.9 volts...so it may be time to think about the upgrade.

I don't understand the difference between how a three wire or two wire look.Mine appears to have the large hot wire and two other wires that plug into a socket at 9 oclock facing it from the front.

[ol Curt]

And I suppose the second part of the question is if mine is a three wire, did they make them with external regulators as mine is still hooked to the original regulator at the radiator support.

[ruffrida2005]

Bob what year is the motor and is it a stock alt? It could be a internal regulator. If it was hooked up as an internal regulator you need to make sure that the wires running from the fuse block are cut off to the Alt or you could burn up your wiring harness. I found out that mine was done like that after I bought it. And well i didn't turn the key all the way off and it burnt my harness up. Your alt is the same as mine is with the internal regulator. not sure if it's a one, two or three. but I know it should put out more then 11.9

[ruffrida2005]

I could be way off though, i cant remember what motor your running.

[No_End_66]

You have a 10dn externally regulated alternator. Pull the regulator and alternator and most parts store can test them both. If either one is bad, a late 70's internally regulated 10 si will bolt right up. The wiring is simple. Hook the alternator up big wire to post, old #1 wire to #1 terminal, old #2 wire to #2 terminal. The wires at the regulator will have to be tied together, #1 to #3, #2to #4.

[Ham-er]

2 wire? There arent really any 2 wire alternators for these trucks.

By that picture it is the older 60's style "external relgulator" alternator(NOT the even older GENERATOR)!

The cheapest thing to try first is to just replace the external regulator(squarish box looking thing mounted on the radiator support).

[fixit-p]

You actually need a fourth ground wire going to the ground post. The newer 10 and 12SI alts are grounded through the case the older external regulated 10DN which is what you have (as No End 66 stated) needs a ground wire connected to the "GRD" post. If the ground wire is there you can disconnect the plug at the alt and jump the "F" terminal to the hot post to full field the alt. Only do it long enough to get a voltage reading because the alt will give you all she has when full fielded.

[DPowers]

Good info here
http://www.persh.org/pickup/UnderTheHood.htm#Alternator

[chopper john]

run a 10si alt look for the brown wire on the regulator plug. when you get the new plug on the alt , the red goes on the back power stud and the white goes to that brown gen light the rest chase them out they are not to far on the harness . your alt is an external alt , but your regulator is probably the one going out . i just did one and it was over powering 16volts . i have pics but im new i dont know how to yet

[chopper john]

[chopper john]

http://s625.photobucket.com/albums/tt331/orozcojuan/

[ol Curt]

Originally Posted by DPowers

Good info here
http://www.persh.org/pickup/UnderTheHood.htm#Alternator

Thanks for hte info guys. Knowing what I have helps me to move forward.

Dpowers, several people have pointed to Persh's site. I must be missing a link on there. All I find are those two pics of the alternator.

[ol Curt]

Does anybody have an original 250 inline that might be able to show where the other end of the ground for the alternator is typically connected?

Thanks!!

[astrochimp]

I did the upgrade Sat.

The ground on my '63 went to one of the mounting bolts of the regulator.

I have a '77 SBC, alt on the passenger side.
Went with a 12SI, as it was $89 at AZ for 94 amp, the 10si was $79 for 63amps. I had to swap pulleys, and find a metric bolt for top mount, and buy a alt plug-in connector ($2.99)

http://www.madelectrical.com/electri...elcoremy.shtml

Used this wiring-
http://www.novaresource.org/alt/12sialt.jpg


I 'think' everything is working. the extremely cheap voltage gauge that was in the truck still reads 12v but I measured 14.3 at the battery.

One tip I read- hook it up, turn key to on (dont start!) gen light should be on, if not something is wrong, fix before starting.


EDIT- as the ground is unused on the 12SI, I 'added' it to the 12+ (red)wire, put it over bolt with the other wire on alt, and at bus bar. Stock wire is a little small, doubling should help some

[ol Curt]

I made sure mine was grounded good today and generator light is still on and still 12 volts at battery. Sounds like it will be a good enough reason to buy one a the end of the week and install.

[ol Curt]

Will my gain (from 55-63 A) be enough to just go with a 10SI? I assume just the newer style alternator with improved charging at idle will be a big boost. Am I correct in that? That would almost be a 15% gain in amperage.

[chopper john]

i have the 10si on my 60 its fine

[fixit-p]

The 10 and 12SI are good alts but if your upgrading I would consider the 12SI over the 10 besides the fact that they can be had in higher amp outputs the alt it's self has been redesigned for better cooling. Here is a good article http://madelectrical.com/electricaltech/delcoremy.shtml

[ol Curt]

Originally Posted by astrochimp

I did the upgrade Sat.

The ground on my '63 went to one of the mounting bolts of the regulator.

I have a '77 SBC, alt on the passenger side.
Went with a 12SI, as it was $89 at AZ for 94 amp, the 10si was $79 for 63amps. I had to swap pulleys, and find a metric bolt for top mount, and buy a alt plug-in connector ($2.99)

http://www.madelectrical.com/electri...elcoremy.shtml

Used this wiring-
http://www.novaresource.org/alt/12sialt.jpg


I 'think' everything is working. the extremely cheap voltage gauge that was in the truck still reads 12v but I measured 14.3 at the battery.

One tip I read- hook it up, turn key to on (dont start!) gen light should be on, if not something is wrong, fix before starting.


EDIT- as the ground is unused on the 12SI, I 'added' it to the 12+ (red)wire, put it over bolt with the other wire on alt, and at bus bar. Stock wire is a little small, doubling should help some

Has anybody else tried the wiring as shown in the novaresource link above? My instructions were a bit different. I capped the red and white off, and connected the blue and brown at the regulator and hooked the blue to the number 2 terminal on the alternator. Can anybody confirm which is correct?

[fixit-p]

Here's a more simplified diagram the important thing is that terminal #1 has switched power through charge light or resistance wire terminal #2 has power all the time and can be connected at the back of the alt but is more efficient if it's wired in at the buss (as kind of pictured).

[ol Curt]

A guy over at the HAMB says it goes like this...does it look right?

[fixit-p]

Yeah thats the same thing, the brown wire is the ign. switched wire which comes from the gen light or resistor wire and goes to terminal #1 to excite the field and the red wire comes from the alt buss and goes to terminal #2 which is the voltage sense circuit

[ol Curt]

I went home and checked mine at lunch today. I actually had it right.But....I don't have 12 volts when switch is on at brown wire.

I hate chasing gremlins

[Ham-er]

Originally Posted by ol Curt

I went home and checked mine at lunch today. I actually had it right.But....I don't have 12 volts when switch is on at brown wire.

I hate chasing gremlins

With a good charge bulb and good ignition switch?
If you checked with everything connected(at the ALT connector),You WONT see 12V there on a volt meter. It would be "grounded" THRU the alternator field coil!
Unplug the connector and then check for 12V(with the ign switch on).
If you still dont have 12V, check the bulb.

[ol Curt]

I found the pink wire on the cluster harness fried. Not sure if it was that way, or I created that! Pics of it tomorrow. I do recall I didn't initially disconnect the battery, and the hot wire from it hit the frame and sparked....possibly enough to cause the meltdown?