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12si classic car 250amp b-stock alternator

$409.00 $239.00
12si classic car 250amp b-stock alternator  30day warranty. 12 and 6 mounts We also have GM ad244 style 250amp b stock with serpentine pulley

12si classic car 250amp b-stock alternator  30day warranty. 12 and 6 mounts

We also have GM ad244 style 250amp b stock with serpentine pulley

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We offer free shipping in the United Status. Orders ship in approximately 5-15 business days, sometimes sooner. If for some reason parts are on back order, we will notify you, but this is not common. If payments are being made on an order, your order begin processing once we receive the order.

Each of our high output alternators come with smaller overdrive pulley. This pulley is made to increase low RPM charging for maximum output. It is custom for the diameter of the overdrive to be less than your factor pulley, depending on the kind of vehicle you own. For this reason, unless otherwise specified, you will need at least a 1/2 inch shorter belt. You can purchase this from any auto parts store. In using the belt and the pulley system, ensure that each part of the pulley system is free of oil or grease, this will help its efficiency.

It is important to make sure that the small regulator plug that is located on the back of the alternator is well plugged in for the correct functionality. Do not forget to plug it in completely, try not to jam the plugs in backwards, and avoid pinching it in order not to create a short. For more information on regulators and wiring see installation instructions.

Our high output alternators come with an overdrive pulley. The pulley is designed to improve low RPM charging so that it yields maximally. Do not change this overdrive pulley out with a larger diameter pulley. When alternator pulley diameter is increased, the output amperage decreases. Changing the pulley will void all warranties.

We offer lifetime warranty on alternator labor and a one-year warranty on parts. All orders are heavily wrapped for shipping with several layers of big bubble wrap and two layers of boxes along with a Fragile sticker on the box. If you must ship your alternator back, please be sure you wrap it the same way to prevent further damage. See more details on our warranty page.

The reason could be one of two things: Either the plug is wired incorrectly or the computer is sensing the higher voltage and causing the battery light to come on even though the alternator is charging properly. Please refer to the instruction manual tab on the website for specific instructions that will help you with wiring. For some older vehicles, the factory style regulator is not available with the hairpin style alternator. This is why your high output alternator will come already “upgraded” with the 15 volt regulator. It will have an oval plug which requires splicing into the factory plug. This is a simple ,fast step and these instructions are detailed for you in the instruction manual.


2012-2021 Jeep Wrangler 250 to 425amp Alternator.

Look and Runs Amazing

Brandon Manis, April 2022

Every single audio build I’ve done always has a JS alternator. Great customer service, amazing pricing, very fast shipping, got my alternator within a week and it’s a pretty rare car so I was surprised at the speed they had my alternator built and shipped out to me. Amazing company and I will continue to use them and represent them on all of my builds, highly recommended and very good quality product.😌 (also their powder coating is perfection)

Very Nice Alternator

Paul Nelson, March 2022

I will not consider going anywhere else for my high output alternators. 10.5kw of bass amps on my daily driver and I do not lose even a thenth of a volt while driving at full tilt! Two vehicles and two alternators and zero problems with the alternators, customer support, or shipping times. Customer for life here! Do not hesitate. 👍

Super Impressed

Kino Hicks, April 2021

Just got mine and super impressed. The customer service was very helpful and I would encourage anyone who needs a high output alternator to use these guys!!!

2012-2021 Jeep Wrangler 250 to 425amp Alternator.

They're so great they even shipped out my made to order alternator on New Year’s Eve.

Petey Parado, May 2021

Ordered my alternator a week before Christmas 2020.They emailed to confirm my address in Hawaii. I emailed back and they responded quickly.There so great they shipped out my made to order alternator on New Year’s Eve. I received it on the 4 of January 2021. It came with everything I needed. Shorter bet I got from local auto parts store.your JS ALTERNATOR made my sound system very happy voltage stays above 14v. THANKS,Jonathan from Kauai Hawaii..


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