Re: 12 Volt Conversion For 46 John Deere B

Posted by Steve - IN on January 20, 2003 at 12:30:04 from (12.222.17.160):

In Reply to: 12 Volt Conversion For 46 John Deere B posted by Jeff on January 20, 2003 at 10:38:40:

Jeff,

Sounds like your alternator might be a 3 wire Delco SI. The R and F terminals are for relay and field. Here's a web page that will give you the details http://www.oldengine.org/unfaq/10si.htm

Your B left the factory with positive ground. The Delco is negative ground. You're going to need to swap the battery polarity to keep the Delco happy, in addition swap from a 6 to a 12 volt battery. If you do try the lights - the 6 volt bulbs will pop fairly soon when you feed them 12 volts. You'll also need to swap the wires going to the amp gauge if you want it to read properly (assuming it's working). The other problem with the Delco is that they like to see a few thousand RPM's before they start charging. Your B only turns 1000 or so and with a 2:1 ratio will only turn the alt at 2000. Two ways to deal with this problem - change the pulley on the alt to a smaller one, or change its internal regulator in the Delco. Also, if you're running 12V the 6V starter will be OK as long as you don't crank for any extended time.

Over the years a lot of 6 volt systems get 12 volt or 4 gauge batt cables stuck on them. That's the kiss of death. It should have 0 gauge or big welding cables hooked from the batt to ground and to the starter. Have you tested any of your current charging system? You can check the generator as follows: Remove both wires from the generator. Run a temporary jumper from the generator F terminal to a good ground. Connect one voltmeter lead to the generator A terminal, and the other lead to a good ground. Now run the engine at about 1/2 throttle. If the generator is a stock 6 volt unit and is working properly, the voltmeter will show somewhere between 12 and 18 volts. (The faster the motor is running the higher the voltage you will read). If the voltmeter reads 0 or close to it, the generator is the problem.

Also, does it have a cutout or a regulator, that is - 2 wires versus 3 or 4 going to the box on the generator. In a pinch you can just wire around a cutout with a switch to keep the battery from discharging at low RPM, and only switch it in at high RPM. Another easy fix is to open up the box and clean the contact points (1 set for a cutout, 2 for a regulator).

Also, here's a link to a wiring diagram for early and late B's. http://www.deerehunters.com/wiringFrame1Source1.htm

Hope that's enough info to get you started. Good luck with the project.

Steve

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