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John Deere Tractors Discussion Forum

Alternator for my JD 401 B

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37 chief

06-06-2020 19:06:02

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If I wanted to install a single wire alternator in my 401B. Is there an alternator from a auto parts store that has similar mounting as the JD? I am sure my 401B is similar to a few ag tractors. Any thoughts? Stan

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06-08-2020 09:43:32

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 Re: Alternator for my JD 401 B in reply to 37 chief, 06-06-2020 19:06:02  
Yes, it can run through an ammeter.

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37 chief

06-08-2020 09:31:22

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 Re: Alternator for my JD 401 B in reply to 37 chief, 06-06-2020 19:06:02  
The wiring on my 401 B is beyond repair. Something I don't want to mess with. I charge the battery every couple days, and I am good to go. If I go with a single wire alternator can I run it through a amp meter? Stan

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06-08-2020 09:53:00

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 Re: Alternator for my JD 401 B in reply to 37 chief, 06-08-2020 09:31:22  
Yes, just use heavy enough wire. If the alternator is capable of 70 amps, it ought to have at least AWG #8 wire unless you protect it with a breaker or fusible link.

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06-07-2020 05:46:32

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 Re: Alternator for my JD 401 B in reply to 37 chief, 06-06-2020 19:06:02  
A single-wire (self exciting) alternator is not a standard used on mainstream cars and trucks or tractors. Many places sell Delco SI or Delco clones from China brand new with one-wire regulators installed. You can buy a brand new, one-wire alternator right here at YT Tractor just as cheap as most other sellers.

Keep in mind - a Delco SI does not have the exact same footprint as the AJ12N Motorola alternator you have now. So a few minor mods are needed to install it. NOTE - the fan belt width. You likely have a 1/2" belt and most of these alternators come with 3/8" pulleys which will not work. Plus, a one-wire alternator has no hook-up for your "no charge" light.

YT tractor sells a new Delco clone from China with the wide pulley you need already installed, and set up for one wire.

I have a Delco SI on my Deere 300B but I used the OEM three-wire hookup to keep my warning light working. 3 wire also charges your battery more accurately then a 1 wire, not that it matters much on a tractor.

DB Electrical also sells them with free shipping and will install the correct pulley if you call and ask.

You can also take the pulley off your Motorola and just stick it on a Delco SI if wanted.

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06-07-2020 05:08:02

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 Re: Alternator for my JD 401 B in reply to 37 chief, 06-06-2020 19:06:02  
Do you have an ammeter or charge indicator light? If you have the light you will need more than one wire anyway to keep it working. 10SI as SVcummins posted is an easy fit. I'm running those on 2030s. Has a spade terminal (#1) for the indicator light wire. #2 spade terminal can be connected to the alternator output stud with a short jumper. The belt pulley for a pickup/auto may not be right for your belt. If that is the case, get a small diameter pulley, the right width, for your belt to get the best results. Small pulley turns the alternator faster at the lower rpms normal with tractor engine speeds.

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06-06-2020 22:18:27

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 Re: Alternator for my JD 401 B in reply to 37 chief, 06-06-2020 19:06:02  
I use a delco ten si three wire on all mine including the combine . The single wires cost more but they are a bit easier to hook up . I just tell the guy behind the counter I need a alternator for 1985 Chevy 1/2 ton pickup with a 350 ( with a lot of horsepower) and he hands me the alternator somewhere around 75$ without a core and lifetime warranty

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