Alt Replacement Options? A bit confused.

geocrasher · Dec 9, 2024

Hey everyone, the alternator died in my 88 Burb with a small block. It's not a serpentine setup, but still looks like a serpentine pully. The truck is intended to go deep into the Nevada desert. I just spent $225 on the best battery I could find under $300, and I want an equally good alternator. Summit Racing has many, and I read about the CS130 upgrade, but when there are so many options, I often get stuck in decision paralysis. I'm unclear what would swap in and which harness I'd need to adapt it. Here are pictures of what's in there now:

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I do realize that the original owner fixed the wiring harness incorrectly but it's never really been an issue. I can buy the proper connector if it's necessary.

Thanks for any suggestions, I sincerely appreciate them.

legopnuematic · Dec 9, 2024

What you have on there is a 12si unit. A little over 90 amp output, a nice improvement over the older 10si units.

Standard (or maybe optional) on the later trucks.

A power master 12si would be a direct swap and I think would provide satisfactory results.

Tonimus · Dec 9, 2024

Summit has a house branded 140 amp 10si pattern alternator. Should be plenty for you. The CS130s are nice, and do go over 200 amps nowadays, but they're also more sensitive. For pure reliability, it's hard to beat a 10/12si. The one I link to is also able to be run as a one wire, so if you're stuck somewhere and need to rig it up, you can.

Summit Racing SUM-810344 Summit Racing™ Alternators | Summit Racing

Free Shipping - Summit Racing™ Alternators with qualifying orders of $109. Shop Alternators and Generators at Summit Racing.

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slammed84 · Dec 9, 2024

I would normally recommend Powermaster, however, the last one I bought already had an audible bearing noise at idle, and still does. But it works. I have also bought some new parts from that TYC brand on Partsgeek and RockAuto and I have always been impressed with the quality. Definitely not the cheapest made parts from overseas, like some other brands.

Amp draw on the alternator is dependent on what electrical devices are optioned and/or installed after factory. If the standard Alternator has held up that long, I don't see the need to spend more on an upgraded current rating unless you plan to digitize some of the controls in the future.

If it were me, I would look for the exact same alternator housing/pulley design and get the best brand that offers it. Oh, and buy the 2 pin pigtail to fix your alternator wiring while you're at it!

geocrasher · Dec 9, 2024

Thanks everyone, this has helped SO MUCH. I do have off-road lights and am adding a winch soon, so I think I'll go with that Summit 140A that @Tonimus linked. Thanks again. And yes, I'll fix the wiring too!

geocrasher · Dec 9, 2024

Well I thought this was solved, but then I looked and the alt linked was for a V belt, and mine has a 5 groove. So I check the other models, the next model number up is a SIX groove pully. *sigh*. The search continues.

legopnuematic · Dec 9, 2024

You should be able to swap the pulleys with the one from your old alternator.

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Ricko1966 · Dec 9, 2024

Running a 1 wire is not a good idea,unless you really have too. I can't see why anybody would have to but I haven't seen everyone's situation. The 2nd wire in the plug on the SI series alternators,is a sensing wire it tells the alternator what the voltage is, at a different point in the system so the regulator can adjust output accordingly. If you are running the second wire to the charge post or running a one wire,you lose the current sensing function. The alternator still charges,but not as GM intended because your alternator can't see all the draw your battery is seeing from the stereo,lights etc.

Camar068 · Dec 9, 2024

Something I found and thought I'd share.

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Snoots · Dec 9, 2024

AD230

75gmck25 · Dec 9, 2024

94 amp 12si is very easy to find, either rebuilt or new. However, mine has a v-belt pulley, so my Lester number (Lester is a standard cross reference number system for alternators) won’t work for your application.

When I upgraded from a 10si I figured mine out using info from the Mad Electrical site. Site can get a little confusing, but I think it has the info you need.

Tonimus · Dec 10, 2024

You can swap the serpentine pulley over to the Summit alternator.

geocrasher · Dec 10, 2024

Thanks again everyone. I was admittedly quite intimidated at the idea of changing the pully until I saw this YT video:

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Well that looks super easy! I'll be buying that correct alternator on Summit, and the wiring harness for it, and swapping the pully. I sincerely appreciate all the help. Keeping these old rigs on the road is a lot of fun, and even as I get closer and closer to 50, I'm learning more about mechanics than I ever did before.

Matt69olds · Dec 10, 2024

Ricko1966 said:
Running a 1 wire is not a good idea,unless you really have too. I can't see why anybody would have to but I haven't seen everyone's situation. The 2nd wire in the plug on the SI series alternators,is a sensing wire it tells the alternator what the voltage is at a different point in the system so they regulator can adjust output accordingly. If you are running the second wire to the charge post or running a one wire,you lose the current sensing function. The alternator still charges,but not as GM intended because your alternator can't see all the draw your battery is seeing from the stereo,lights etc.

People run one wire alternators for one of 2 reasons: because they don’t understand how the charging system works, and are too stubborn to learn, or because they don’t understand the benefits of just repairing the system GM designed into their vehicles.

Losing the remote voltage sense is one big disadvantage, another is the loss of the charging system warning lamp. Granted, most GM trucks have a volt gauge, but it’s hard to argue that a big red light will grab your attention far sooner than a gauge will.

Tonimus · Dec 10, 2024

Matt69olds said:
People run one wire alternators for one of 2 reasons: because they don’t understand how the charging system works, and are too stubborn to learn, or because they don’t understand the benefits of just repairing the system GM designed into their vehicles.

Losing the remote voltage sense is one big disadvantage, another is the loss of the charging system warning lamp. Granted, most GM trucks have a volt gauge, but it’s hard to argue that a big red light will grab your attention far sooner than a gauge will.

Just to be clear, I was not advocating the use of one, just that it could be handy in an emergency to get you out of a jam.

Alt Replacement Options? A bit confused.

geocrasher

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