smaller alternator pulley, yes again.

[fredsterra]

I put one on mine years ago. Sorry I don't have a number for it. But it was about 1/2" smaller in dia.

The alt. puts out the same amps. But at idle with ac and lights it will hold almost 13.5 volts.

And about 2 years ago I replaced my amp gauge with a volt meter. With the blinkers on with full load it will bounce from about 13.5 to a tick over 12 at idle.

[Eric VanBuren]

Originally Posted by curt

they have been new, off the shelf Ultima units, not sure of the si. and the last couple of units only seemed to last 2-3 years. that is the root of this problem as the unit i have now was not charging anymore. when i pulled off the current pulley it fell apart on me, hence me need for a new one.

so i have found a replacement OE pulley, as I want to keep the double belt option. If i put this on the 85amp alt(already secured the replacement), will i have possible wiring problems? or should i go back and get a 63 amp 'stock' size?

prior to all of this, my dimming issue wasnt that great. just more or less at idle when the a/c was on, headlights and radio. If I remember correctly, the gauge(ive got an aftermarket unit installed) read 11/12 with all that on, and when everything was off at running speeds it read around 13/14. Turning the curb idle up is probably a great suggestion as i hadnt tried that before.

The new Ultima alternators are made in China and if you are getting 2-3 years out of one you are doing good. What part number is it?

So you don't have an ammeter any more? That will tell us exactly what is going on, a volt meter not so much.

A 85 amp alternator is a little much for the factory wiring which is set up for a max 61 amp alternator.

[RD Durham]

Look for late '70s or early '80s Ford pickups to get a smaller double pulley. The inside diameter of the pulley has to be 0.670" (17mm).

Try this website:

ASC Supply - Alternator Pulleys

[curt]

alright, seems i was working with the wrong stuff all this time for sure. previous owner snafu! I had no idea. but i thank all of you on this post for getting the gears turning in my head.

I found through Mark at ScoutMADness an original OE pulley that was 2" at a VERY reasonable price comparitively. from there I just ordered me a stock sized alternator, hooked it all up and wah-lah...no more dimming at idle and a good level constantly. bright interiors, the works! i dont even have to jimmy the mount with a dremel and washer anymore to make the larger alternator fit. easiest alternator swap i have ever done to the truck.

Now i am cornfused about the logic of the larger pulley. I even pulled the old alternator from my parts 71 Travelall and it had the same 3.5 pulley with what seems to be the same size 'stock' alternator. Hmmmm.....

[BO185]

Curt, Did the 2'' pulley come with a part number brand?

[curt]

Originally Posted by BO185

Curt, Did the 2'' pulley come with a part number brand?

it did:

Delco-Remy GM 1852856

[Joe D.]

Originally Posted by curt

Now i am cornfused about the logic of the larger pulley. Hmmmm.....

I think this is an example of the farm tractor engineering that we love and hate about our IH rigs. The alternator mount is not particularly well designed. It can be hard to get the alternator belt tight enough to prevent slippage. Rather than design a better mount, they went with a large diameter double pulley. Large pulleys let the alternator turn slower, requiring less torque to turn, equals less slip. Also, since the belt doesn't have to be as tight, the bearings and bushing might last a little bit longer. Or so the thinking must have been.

[Jay Tabor]

alternators tend to put out a lot of amps at lower rpms, thats kinda why all the auto manufacturers went to alts from generators, which need a higher rpm to get close to the amps an alt. puts out at a/the lower rpm.
if your amperage load is up near 60 amps while running, the alt will have to spin at around 1500rpms anyway to try to keep up with the load put upon it . . . . so smaller pulleys arent needed . .
prolly gots you an 'lectric disharge somewheres in the scout,
like the 3500 watt stero amplifier,
the 150 watt subwoofers and bass speakers you gots playing at maximum,
the hydraulic pumps for your lowrider,
the lectric seat warmers,
and the lectric cofee mug . .
plus your three cell phone chargers,
lectric door locks
and auto alarm..
or it could be the bulky connector everyone keeps talking about . .
the ammerator could be bad and lettign those nasty evil amps out into the cab . .

[Bill usn-1]

The light line power was pulled from the medium duty trucks.
The trucks operate at or near full throttle all day long.
Which is near 4000 rpm.

There is no need to run the alt at high speed all day long so the pulley is larger to slow down the rpm.
A car operates at about 2000 rpm on the highway and rarely exceeds 3000rpm.
So the passenger car has a smaller pulley to increase it's rpm at normally operating speeds.

It is farming/truck engineering but in reverse.
As the lightline progressed the alt pulley got smaller and the waterpump and crank pulleys also changed sizes on the SV engines.

[Erik VanRenselaar]

Originally Posted by curt

it did:

Delco-Remy GM 1852856

That's the same part number on the pulley I sourced about 17 years ago.