97/98 vs 99 alternators

So, what changed from the 97/98 alternators to the 99 unit? Looking them up on NAPA online, the 97/98 are 140 or 150 amp, but the 99's are only 125 amp. I'm beginning to suspect mine is on it's way out, judging by the occassional noises from that specific area upon startup. I see Ed M has a couple for 45-65 bucks, from a 97.

i thought they all had 140 amp alt's, and the 150 is an optional HD version from napa.
never heard the 99's were 125 amps, but i just checks and autozone shows the same thing

wonder what the L32 engines use?

Ha! '98s are the best Rivs! FInally!

IIRC the '99s have a different case/mount than '97-8.

I am not sure 140 vs. 125 buys you anything until you start making electrical mods. I think it bought GM fewer SKUs to track. I imagine 140 may have been overkill for the '98 Riv but not for, say, '98 vehicles with more accessories (minivans wth dual air conditioning?) using the same engine/transmission.

If you have access to a bearing press, why not replace the alternator bearing and brushes yourself?

And if you are going to get a rebuilt, consider getting a Delco. I read that the Delco folks use the same rigs to remanufacture the alternators as were used to build and test them in the first place, and that they are definitely as good as new. Last time I replaced an alt, I think last year, I used a reman Delco from gmpartsdirect. They mademe a little mad though, the one they sent me, it loked like they played catch with it before they sent it to me, the pulley was dented. So I used the ol' air impact wrench and pulled the pulley off my old one and put it on the reman unit. (you have to use an air wrench to get the nut off... inertia is your friend...) They did not scream about it when I returned their banged up pulley with the core, althoug I admit I warned them via email.

Albertj

Oh I don't know, the extra 15 amps could certainly make a difference. When I'm stuck in traffic in the snow, wipers running, Front and Rear defrost on high, heated seats, lights on... my lights start to dim and the wipers slow down in my '98... Here's wishing I had a 160

Maybe I don't have the original alternator anymore!

How does one load-test an alternator and find out it's full capability?

take it to autozone and they can test them. unfortunatly i think it needs to be off the car.
we used to test the entire electric system at pepboys. alt, bat, load, cell cap., and some other stuff.
as far as a DIY test IDK.

albertj wrote:

If you have access to a bearing press, why not replace the alternator bearing and brushes yourself?

I don't, and this is my DD so an extended time in the garage is not an option right now. I'm by no means certain that it was the alternator that was noisy, but it seemed to originate there. No noise for several days now though. There's one on ebay from a 97 that has a "reman. for AC Delco" label on it, with 70k on the CAR. Was contemplating that option just in case. BTW, the original GM part # for a 98 alt is no good on gmpartsdirect.com.

140 amps might be overkill, but you can never have enough amps. There's no downside because the car only uses as much current as it needs.

you could always get the 150amp and then buy the zzp underdrive pulley
or does that just decrease voltage?

The underdrive creates more current I believe, at the expense of shorter alternator lifespan.

I thought the underdrive pullies were to slow the alternator down. Amp production would be less, but freeing a few HP. Same with the water pump underdrives - slow down water pump, free up HP.

I was considering an alternator OVERdrive pulley which would shorten alternator bearing life, but produce better voltage at idle... but I haven't done that yet.

Right, underdrive(larger) pulleys reduce parasitic power loss, whether for alt or water pump, etc. Accessory turns slower, uses less hp.

You can overdrive your alt with a smaller pulley, just like the SC, with a smaller pulley. The alt turns faster for a given engine RPM.

I think that's what Matthew meant, but you're right, it's overdrive. The problem with overdrive pulleys, the alternator's internals are still build for their original rating.

If you want higher voltage, insert a diode inline with the sensing lead of your alternator.

Do the 96-99 Rivs have the sensing wire? B'villes don't, however recent tests by crackhead B'villers show that adding one from a +12V source in the loom behind the alt will bring it up in voltage.

For example my alts always read 12.7-13.2 and this bothered me. Add the sense wire and I'm running 14.5 consistently. Only thing to keep in mind is when you are sitting at that light with every electrical gizmo on .. you aren't generating much power and voltage will drop. Even a buddy with a 2003 has that issue.

B'villes came stock 96-99 with 140 amp. It's nice..however low engine rpm doesn't help. I've considered overdriving. Theoretically it's no different to the alternator than someone that mods heavily and takes their car to 6000-7000 rpm frequently. (Why are you guys looking at me like that?

As far as I know alternators on '96 up have the sensing wire. It leads to the battery to monitor temperature. If the battery gets hot, voltage is decreased. It's easy to slip a diode inline with this wire to get 14.5-14.9 volts. See link:

https://rivperformance.editboard.com/audio-electronics-f7/write-up-stage-i-voltage-booster-t1610.htm#27955

I agree running an alt overdrive pulley isn't a bad idea, as long as you do supporting mods (upgrade the diodes and other goodies inside the alternator). Otherwise it's like hitting 6kRPM with stock valvetrain.

Well this issue was resolved nicely. After work I took the accessory belt off the tensioner pulley, and found the bearing in the tensioner pulley was in very poor shape. As I already had all the new pulleys on hand, a quick swap to the new metal 38006 quieted things down nicely. No more noise and the alternator pulley felt good too. I'll start a new thread for my newest problem...

I bought a Delco reman alt from gmpartsdirect last year. p/n was 10463691.

By the way, for those of you using synthetic oil, an oil cap (actually for corvette) with "use only Mobil1 5W40" printed on it is p/n 12555685. I bought one and put a permanent label on it changing 5W30 to 10W30, for the Riv. It's kind of a running joke between me and the service manager at the dealership I sometimes take the car to. One time I hd them change oil and I'd asked for 10W30 synth, they put 5W30 dino oil in. How could I tell - it ran differently. Service manager says, 5w30 is what we put in all the engines. I says, okay but the owners manual says 10w30 and unless you have a service bulletin that makes the change, although the likelihood is small are you gonna take responsibility of something goes wrong and the problem is attributed to the wrong oil fill? and if not, then let's clean this up now and put the correct weight oil in there. So when I go pick up the car, he's had the techs put a sticker on the cowl (same as the Vette) to only use Mobil1. We had a good laugh about that when I picked up the car. So when gmpartsdirect was getting rid of the printed caps, I bought one.

I also noticed the price of the center caps of the chrome wheels is up to 83.20 retail / 51.07 net. When I bought in late 2005, net was $34.66 - ouch! They must have decided to have some more made, or some such.

Back to alternators - next time I have to buy one, unless the core is generous I'm keeping it. There is a technician we call "Cajun," a retired Navy mechanic, who (provided he can get parts) can repair just about any small motor or generator. [Cajun Starter & Alternator Service (607) 295-7794 42 West Ave, Arkport] If you can get it to his shop in Arkport (in a farming area about an hour west of Corning, NY), he can probaby fix it. Given that the dying part on our alternators is often just that *&^@#*$ bearing, having Cajun crack it open and repair it sounds good to me.


Have to run

Albertj

Alternators are really not that complicated inside, and there isn't a lot to replacing the bearing. Problem is you can't get the bearings easily.

Years ago they had 'rebuild kits' for alternators...

RockAuto.Com had the bearings, brushes and other items as service parts last time I looked.

Albertj
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